Curt Flex Air Pin Box for Lippert 1621: Fitment and Shipping Information
Updated 07/09/2026 | Published 07/01/2026
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Question:
I’m looking at the curt flex air pin box That fits the lippert 1621 How will that be shipped to North Vernon IN 47265 Obviously, too heavy for ups or fedex
asked by: James V
Expert Reply:
Hi James,
If your fifth wheel has the Lippert 1621 bolt pattern, you're looking at the right style of pin box. There are two Curt Flex Air options that fit the 1621. The 18,000 pound model is part # LC328492, and the 21,000 pound model is part # LC369535. I think the Curt Flex Air is an excellent upgrade because the pivoting head helps reduce the chucking you feel when the trailer pushes and pulls on the truck, especially over bridge joints and rough roads. It also has a built in rubber cushion that absorbs bumps and vibration before they're transferred into the truck and trailer, making for a much smoother ride.
As for shipping, you're exactly right. It's much too large and heavy to ship by UPS or FedEx, so it will be sent by LTL freight on a pallet. The freight carrier will contact you ahead of time to schedule a delivery appointment, so you won't have to worry about it showing up unexpectedly. Shipping it by freight also does a much better job of protecting it during transit since it's secured to a pallet instead of moving through a standard package handling system.
Out of curiosity, where do you like taking your fifth wheel once everything's hooked up and ready to go?
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Product Page this Question was Asked From
Curt Flex Air 5th Wheel Pin Box - Lippert 1621 - 21,000 lbs
- 5th Wheel Pin Box
- Upgraded Pin Box
- Absorbs Road Shock and Reduces Chucking
- 21000 lbs
- Air Ride Suspension
- Fixed Turret
- Lippert 1621
- CURT
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on 5th Wheel Pin Box
Lenard P.
7/8/2026
James, bought the Curt pin box last year. Seams to really help the chucking. When you install it the holes don't line up exactly so leave all the bolts loose until they are all started. After I installed it I had the local shop inspect it because it looked like on an angle but found it was the design to accommodate the extra room needed for the air bag. Put mine on with a small tractor, it is heavy. I have a 2023 Ram 3500 dually with a 2022 Heartland 45' Cyclone. Good luck you'll need it to install it but you will be happy with it.