What Is Difference Between An 18K Flex Air Pin Box And 21K Flex Air Pin Box

Published 07/16/2021

Question:

what is the difference betwen a 18k and the 21k because my fifthweel is a cruiser model 322rl and the weight is 12500 may be the 18k work better

asked by: Ghislain L

Expert Reply:

The difference between the 18K and 21K Flex Air pin boxes is the weight capacity. Manufacturers recommend only using 80-85% of the maximum weight capacity. 80% of the 18K pin box is 14,400lbs so you'd be able to load in another 2000lbs of stuff and still be in the 80-85% range. It wouldn't hurt you go higher with the 21K pin box but it isn't necessary.

When it comes to picking the correct pin box for your trailer you will need to match the bolt patterns. The Trailair Flex Air 5th Wheel Pin Box - Lippert 1621 - 18,000lbs Item # LC328492 you linked to was designed to replace 1621 style pin boxes. If you need help determining the pin box that you have please reply back with any serial numbers you see on the side or front of the pin box and I can find the correct fit for you.

expert reply by: Kevin C