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  1. Fifth Wheel King Pin
  2. Lippert
  3. Lippert 1621
  4. Lippert 1621HD
  5. 18000 lbs GTW
  6. Upgraded Pin Box
Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD - 18,000 lbs

Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD - 18,000 lbs

Item # LC328330
Our Price: $645.56
You Save: $255.25
Fifth Wheel King Pin
Shipping Weight: 97 lbs
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This Rota-Flex pin box has a pivoting head with a built-in rubber compound that works to reduce chucking and absorb road shock, resulting in a smoother ride and less wear and tear on your trailer. Replaces Lippert 1621 or 1621HD pin boxes. 1-800-940-8924 to order Lippert fifth wheel king pin part number LC328330 or order online at Free expert support on all Lippert products. Great prices and Fastest Shipping for Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD - 18,000 lbs. Fifth Wheel King Pin reviews from real customers.
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  • Reviews (46)
  • Q & A (0)
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Lippert Fifth Wheel King Pin - LC328330

  • Lippert 1621
  • Lippert 1621HD
  • 18000 lbs GTW
  • Upgraded Pin Box
  • Lippert
  • Absorbs Road Shock and Reduces Chucking
  • Fixed Turret

This Rota-Flex pin box has a pivoting head with a built-in rubber compound that works to reduce chucking and absorb road shock, resulting in a smoother ride and less wear and tear on your trailer. Replaces Lippert 1621 or 1621HD pin boxes.


  • Pivoting pin box replaces standard pin box on your 5th-wheel trailer to improve handling and limit strain on the truck and trailer
    • Minimizes chucking by allowing controlled movement of king pin within your hitch
  • Rubber compound built into the head absorbs road shock
    • Reduces wear and tear on trailer
  • Black powder coat provides rust resistance
  • Sturdy steel construction
  • King pin connects to any 5th-wheel trailer hitch
  • Bolt-on installation with no assembly required
  • Made in the USA


  • Designed to replace Lippert 1621 or 1621HD 5th-wheel pin boxes
  • Weight capacity: 18,000 lbs
  • 1-Year limited warranty

Diagram of measurements for the Lippert Rota-Flex pin box


  • Do not use the Trailair Rota-Flex pin box with any type of gooseneck adapter.
  • The Trailair Rota-Flex is not compatible with Curt E-Series or Q-Series 5th wheel hitches.

The Rota-Flex pin box has a pivoting head and built-in rubber compound that help to reduce chucking and absorb road shock for a smoother ride as you tow your fifth-wheel trailer.

Pivoting Head Reduces Chucking

The Lippert Rota-Flex pin box has a pivoting head to help reduce chucking

The pivoting head on the Rota-Flex allows for controlled back and forth movement of the king pin to reduce the uncomfortable jarring known as chucking. Unlike a rigid pin box that has little give at the point where the trailer and the hitch are connected, the Rota-Flex can pivot slightly to compensate for those times that your trailer suddenly pushes or pulls on your tow vehicle. Because the pin box head - not the king pin itself - is moving, the chucking that often occurs when the king pin jerks around inside the hitch is significantly reduced.

Rubber Compound Absorbs Road Shock

The Lippert Rota-Flex pin box has a built-in rubber compound to help absorb road shock

A heavy-duty rubber compound is built into the head assembly of the Rota-Flex pin box. This rubber absorbs the bumps and vibrations, or road shock, experienced when towing a fifth-wheel trailer over rough roads. Standard pin boxes without any type of shock absorption transfer road shock to your trailer, resulting in potential damage to the trailer and an overall bumpy ride. The shock-absorbing rubber inside the Rota-Flex takes the beating so there's less wear and tear on your trailer or RV and you get a smoother ride.

Easy, Bolt-On Installation

The Rota-Flex is easy to install. Simply remove your existing Lippert 1621 or 1621HD pin box and install the Rota-Flex on your trailer or RV. The Rota-Flex uses the same bolts that held on your original pin box so no additional hardware is required. Plus, it comes out of the box ready to be put on your trailer, so no assembly is needed. Because the Rota-Flex is quite heavy, you should put it on an elevated surface or have a friend help you support its weight during installation.

328330 Lippert Components (LCI) Rotaflex by Trail Air Fifth Wheel Kingpin Box for Lippert 1621 or 1621HD

Replaces UF35-946202 Ultra-Fab Rubber Ride Kingpin Box by Rota-Flex

Installation Details LC328330 Installation instructions

Customer Satisfaction Score:

Customer Reviews

Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD - 18,000 lbs - LC328330

Average Customer Rating:  4.7 out of 5 stars   (46 Customer Reviews)

This Rota-Flex pin box has a pivoting head with a built-in rubber compound that works to reduce chucking and absorb road shock, resulting in a smoother ride and less wear and tear on your trailer. Replaces Lippert 1621 or 1621HD pin boxes.


The shipping container was not adequate for pin box. It was too large and no protective packing was used to protect the powder coated finish. When it was delivered by UPS the carton was destroyed. I had to repaint it as it was badly chipped from rough handling. I am disappointed in the performance as I do not see any difference in the chucking which is the reason why I purchased it. If I were to get a different 5th wheel I will not purchase a Rota-Flex again.

Etrailer Expert

Katrina B.


With the Rota-Flex, it is meant to reduce the amount of chucking that comes with hauling a 5th Wheel trailer. However, there are a lot of factors that can be the cause of chucking, such as: the nose being high or the nose being down, too much weight in the rear of the trailer, or even a 5th Wheel hitch that has a more loose or lower tolerances in the jaw. Due to all of these factors, you might not be able to notice any difference or the chucking can even become worse, depending on the situation. I also see that you have received some damage to your pin box, when it comes to shipping, it is possible that the pin box could have been scratched. We recommend using a rust-oleum type of paint to prevent any corrosion. I have a link below for your reference. I have also sent this information over to our customer service team for them to better assist you.


Received on Wed. as planned. With a little help from my forklift, I had this trail air pin box installed in few hours. Fit perfect on my Sabre. Drove around the block, about 4 miles. This pulls so nice, it is like nothing behind you. Thanks etrailer.


Looks great on my 5th. If anyone else has wondered as I did and could not find anything online regarding the vertical height difference between this trail air rota flex and my standard lippert 1621. This pin box will reduce the nose of my 5th by 2" mounted in the same location. Now to pull my rear axle spacers on my dodge to get another 1.5" lower. Etrailer is great as always. Never had a problem with them and have ordered here many times. Thanks Etrailer!


The product was great, The better part was how fast it got to me . I had it put on the camper the same day i had received it what was 3 days after my order. Now you can't beat the shipping. All my orders from ETrailer has been fast and on time . Thank you all at Etrailer.


I was surprised at the difference one product could make in my towing experience! It really helped the chucking.


The difference now compared to when I had my done is like night and day, no more chucking, very little if any jarring , the ride meets al my expectations


Fast shipping and item fits perfectly. Replaced old pin box by myself with a small tractor in about 45 minutes. Can't wait to try it out on my new toy hauler.


A noticeable improvement over the standard pin box. It's most obvious when starting and stopping. It was very easy to install even for two 60+ women. We're happy with the purchase.


The Trailair Roto-Flex is an excellent product. It really has smoothed out the ride and handling of my fifth wheel, especially over roads that aren't so perfect. I highly recommend this for an upgrade.


This king pin assembly works well to get the chucking down. I do feel at times do to road conditions that I still feel some, but over all it has helped the ride and I feel it has take some abuse away from my truck and the trailer seems to ride better. Overall I am pleased with the kingpin assembly for the cost. The only thing I cannot do is put my cover on that was on my old kingpin.


Great customer service and timely shipping.
was as expected.


Fast Shipping,Great product,It sure softens up the ride! Doesn't eliminate all the jerking but overall quite satisfied! Quality built product. Definitely not a one person job so seek out a helper to hold things Thanks Etrailer.



This king pin box came on my 5th wheel, it does not help the jerking at all. I am now looking to install a different pin box.

Patrick B.


Thanks for the feedback. If you need help finding a different pin box, please let me know. We carry Ultra-Fab, Fifth Gear and Reese pin boxes in various versions.


I received my order promptly, faster than expected for a large item. I paid for my pin box, checked the next day and etrailer had dropped the price, they refunded the difference which impressed me greatly. I am a repeat customer and have not had a bad experience ever.


as Always one and done. keep it up


Came in mail packaged! Even the UPS man told me how etrailer is a legit company doing a great job shipping! Any in costumer service was great and her team had the price match over amazon done in one business day. Great to work with!!


The Trailair Rota-Flex pin box worked great. The pin box did the job by removing 80% of the chucking as we traveled.


Worked fine, easy to install only used for one trip to Michigan and sold trailer.


Chelsea was very helpful and the product is very good. The Roto flex was very easy to install Great product.


Received the Roto flex pin box I ordered from etrailer in about a week. Arrived in good condition and perfect fit completely satisfied with etrailer on this order


I haven't opened the box yet, but it was shipped as fast or faster than I ever thought possible. As far as the product goes i am sure it arrived safe and sound. Good job!


I purchased it as a direct replacement for the damaged on on my fifth wheel.


The Roto Pin Box has eliminated 90% of my chucking. The only time I get any now is on a extreme bump but it settles down pretty quick. It was also very easy to install. Some of the bolts are a little tight to get to but doable.


Had trouble receiving the hitch through UPS (they lost it --[48 miles from my residence] conversation with Stacy at etrailer and they shipped another, which my wife and I installed. etrailer was very helpful in sending another to replace the one UPS lost. Thanks so much


It got lost by UPS, but the service and customer service was great, received my product in excellent shape. This is a very good company to do business with. I will do business with them again. Thank you Paul.


Was very to install. Helps a lot when towing. Great pin box.

Show More Reviews

See what our Experts say about this Lippert Fifth Wheel King Pin

  • Pullrite Capture Plate for Rota-Flex Pin Box
    Per PullRite, measure from the front edge of your Trailair Rota-Flex Pin Box, # LC328330, to the leading edge of the king pin plate. If that measures 5-3/8" you need capture plate 331707. If it is 5" then you need capture plate 331760. This is not an item etrailer carries but you can purchase directly from PullRite.
    view full answer...
    Image 1 for Image 2 for Image 3 for
  • Correct PullRite Adapter Plate to Use with Trailair Rota-Flex for Lippert 1621 or 1621HD Pin Box
    According to the PullRite site it looks like you'll need their adapter 331760 to use with the Trailair Rota-Flex part # LC328330 you're looking at.
    view full answer...
  • Is Lippert 1621 Pin Box Different Height from Rota Flex that Fits 1621
    We've spoken with Trailair in the past about this exact question and the Rota-Flex part # LC328330 is going to sit right at 1 inch lower than the 1621 pin box you have currently.
    view full answer...
    Image 1 for
  • Pull-Rite Capture Plate for a Rota-Flex
    From Rep at PullRite, you will need to measure from the front edge of your king pin to the leading edge of the king pin plate to identify which you should use with your Rota-Flex 5th Wheel Pin Box and #LC328330. See the attached image I provided with this, if that measures 5" then you need capture plate 331760. You can acquire this from PullRite.
    view full answer...
    Image 1 for
  • Using Trailair Replacement King Pin with Andersen Ultimate Connection
    I checked with Andersen and they do state that their Ultimate 5th Wheel Connection can be used with the Trailair Rota-Flex 5th Wheel Pin Box like the part # LC328330 that you mentioned. As you referenced, you will just want to use the Rota-Flex Lockout Kit to prevent the rubber pad from shifting over time. We do not currently have this part available. The Trailair Rota-Flex Pin Box is a great pin box replacement that features a pivoting head and a built-in rubber compound that will work...
    view full answer...
  • How Much is the Head Supposed to Pivot on Trailair Rota-Flex 5th Wheel Pin Box
    The head on the Trailair Rota-Flex 5th Wheel pin Box # LC328330 referenced in your question is designed to pivot slightly where the trailer and hitch are connected. This subtle pivot allows for controlled back and forth movement to reduce jarring and chucking, ultimately resulting in a safer and more comfortable ride. The skid plate on the pin box is still going to be quite stiff by design. Light jarring experienced while towing will not move this plate very much but any chucking experienced...
    view full answer...
  • What Rota-Flex Pin Box do You Recommend to Replace my 1621HD Model from Lippert Components
    I really like the Trailair Rota-Flex 5th Wheel Pin Box part # LC328330. It is a confirmed replacement for your 1621 HD pin box and has an 18,000 lb. weight capacity to cover your GVWR of 17,000lbs. Check out the linked video I made on the Rota-Flex. It was a nice improvement to the ride quality and did a good job of reducing the chucking. Check out the video for footage of it in action to actually see how it works. I like the fact that there is nothing to maintain and that the cushioning...
    view full answer...
  • Shape of Trailair Rota-Flex King Pin
    The king pin on the Trailair Rota-Flex 5th Wheel Pin Box # LC328330 features an industry standard king pin. I have attached a photo showing what an industry standard king pin. The photos show the pin box from several different angles and the entire kind pin is not visible in every photo.
    view full answer...
    Image 1 for
  • Changing the Rubber Jounce Stops in a Rota-Flex Pin Box
    I can tell you the procedure for replacing the jounce stops on the Rota-Flex pin box though the exact replacement parts are not available like you said. They are a rubber compound but the specifics of it I do not know. 1. With Long Needle-nose pliers, from the back of the pinbox, squeeze tag ends of Cotter Pin together and push it out of the Front Jounce Stop and it’s channel. Cotter Pin may need to be pulled out from the front of the pinbox to completely remove it from the Jounce Stop. 2....
    view full answer...
  • Difficulty Getting Jaws to Open on B&W Companion Hitch with Rota-Flex Pin Box on Trailer
    The king pin on the Rota-Flex pin boxes does pivot and if you are parked on uneven ground then it is possible that the hitch jaws are bound up some. Moving the truck and trailer to level ground or even pulling forward or backward a little could be enough to release the tension and make it easier to uncouple the trailer. There isn't any sort of adjustment you can make on the pin box that would help. You could also try lubricating the moving parts of the hitch to make them easier to operate....
    view full answer...
  • How to Determine What Pin Box a Trailer Has to Pick Out Replacement
    Sounds like you are looking for a pin box replacement. We don't have a way to determine what pin box your trailer currently has so we'd need you to get the pin box model and number off of it and we can pick you out the correct replacement. Can you check out what you have looking for any models or part numbers and get back to me with that info? Or you can check out the help article I attached on how to measure and determine what pin box you'd need.
    view full answer...
  • Warranty on the Trailair Rota-Flex 5th Wheel Pin Box
    The Trailair Rota-Flex 5th Wheel Pin Box # LC328330 has a 1-year warranty according to the manufacturer. This pin box is designed to replace a Lippert 1621 or 1621HD 5th wheel pin box so you'll want to make sure that's what you have by checking out the sticker or placard on your current pin box. I've added a link to a video review for you to check out as well of the Trailair Rota-Flex 5th Wheel Pin Box # LC328330.
    view full answer...
  • Can Pullrite 2400 be Used with RotaFlex Cushioned Pin Box
    Yes, you can use the Rota Flex pin boxes like the part # LC328330 with a Pullrite 2400 but you will need to use their specific Isolator for this application that we do not carry since we don't carry the Pullrite brand.
    view full answer...
  • Will the TrailAir Rota-Flex part # LC328330 Work on a 9,000 lb Trailer with a 1621 Pin Box
    Yes, the TrailAir Rota-Flex part # LC328330 would work perfectly on your trailer that weighs 9,000 lbs and has a Lippert 1621 pin box currently. Having a pin box that is rated for higher than what the trailer weighs is perfectly fine and definitely preferred over one that is underrated. This will also work well with your 16k fifth wheel hitch.
    view full answer...
  • Rota-Flex King Pin to Replace Lippert 1621HD Pin Box
    I verified for you that the correct replacement for your Lippert 1621HD pin box is the Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD # LC328330.
    view full answer...
  • Pullrite Capture Plate to Use with Flex Air Pin Box
    While we don't carry Pullrite we have looked into this before and the correct capture plate to use with a Flex Air pin box like the part # LC328330 is the part number 331761.
    view full answer...
    Image 1 for
  • Length of King Pin on Lippert 1621 Pin Box
    I believe you are simply asking the length of the king pin on the Trailair Rota-Flex 5th Wheel Pin Box # LC328330. I reached out to the manufacturer who said that the king pin on this pin box measured 3.29 inches. I have added a photo showing other dimensions of this pin box for you to take a look at as well; this pin box is a direct replacement for Lippert 1621 and 1621HD pin boxes and is designed to make your towing experience more comfortable with the rubber compound in the pin box...
    view full answer...
    Image 1 for
  • Torque Value of Hardware for Trailair Rota-Flex 5th Wheel Pin Box
    Please see the linked installation instructions for the Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD, # LC328330 for proper torque values based on your hardware bolt size and grade.
    view full answer...
  • Is The Rubber Cushion In The Lippert Trailair Rota-Flex Pin Box Replaceable
    The cushion block on the Trailair Rota-Flex 5th Wheel Pin Box # LC328330 is not a replaceable part so I would first reach out to Lippert directly to see if this would qualify for a warranty replacement. If not you'd be looking at replacing the entire pin box. To do this you would have to first determine the bolt pattern. There's typically a sticker that has a serial number and RPO number that we can use to verify the bolt pattern, otherwise you'll need to follow the steps listed in the...
    view full answer...
    Image 1 for Image 2 for Image 3 for
  • Mounting Reese Sidewinder Pin Box on Trailer
    I'm not quite sure what you mean by only using only one row of bolt holes when installing the Reese Sidewinder King Pin # RP61410 in place of the Fabex 500 on your trailer. I looked through the installation instructions and it recommends taking note of the number of bolts that were used to attach the factory pin box and use at least this many when installing the Sidewinder turret. I simply recommend bolting up the Sidewinder in the same manner that the Fabex unit was mounted to ensure...
    view full answer...
  • Does Trailair Rota-Flex Work With Curt A-Series 5th Wheel Hitch
    Yes, the Curt A-Series of 5th wheel hitches - including your Curt A16 sliding hitch - is 100 percent compatible with the Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD - 18,000 lbs # LC328330. It is the E-Series and Q-Series that the Rota-Flex is not compatible with, and that is because the head units on those hitches are spherical, which means they don't offer enough stability to be used with the Rota-Flex's cushioning. But the A-Series has a different, upgraded type of...
    view full answer...
  • Compatibility of Lippert Trailair Rota-Flex # LC328330 with Long Bed Truck
    The Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD - 18,000 lbs # LC328330 is compatible with both long and short bed trucks. The turning clearance will be determined by the 5th wheel hitch. I recommend using a sliding 5th wheel hitch with a short bed versus a fixed hitch with a long bed. The Trailair Rota-Flex pin box will work well for you as long as you have a 1621 or 1621HD pin box you are wanting to replace. the Rota-Flex uses a pivoting head with a rubber compound...
    view full answer...
  • Measurement From King Pin Base To Front of Trailair Rota-Flex Pin Box # LC328330
    I went out to our warehouse to take the measurement and the Trailair Rota-Flex 5th Wheel Pin Box - Lippert 1621 or 1621HD - 18,000 lbs # LC328330 is 4-1/2 inches from the front base of the king pin to the front of the pin box when you measure for the straight distance. If you follow the curve of the plate it measures 5-3/8 inches. I've attached a photo to assist.
    view full answer...
    Image 1 for
  • How to Pick Out Replacement Pin Box for Trailer
    If you have to replace your pin box now would be a great time to go with a cushioned one. The Rotaflex like the part # LC328330 would be a great option as long as you have a Lippert 1621 or 1621HD pin box. This is a very common pin box so there is a great chance this is what you would need. You will need to verify your pin box brand and model number before you order though to make sure this would fit. There should be a plate or sticker near the pin box with this info listed. If you have...
    view full answer...

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