https://www.etrailer.com/Trailer-Suspension/Redline/APUBR-9.html
Today on our fifth wheel trailer we’ll be installing the Red Line U-Bolt Kit for mounting 5,200 pound to 7,000 pound round trailer axles. This is part number APUBR-9. Here’s what our kit consists of. We have the two flanges here that will go on top of our axle which will secure our u-bolts to the top and hold our axle in place to release springs. We have the necessary two, one per side and then the necessary four u-bolts, and then the eight nuts to secure it. The reason you want this is in case you ever need to replace a bent or damaged u-bolt or hanger assembly, or if you ever need to remove one a lot of the times they have a nylon lock nut on and you cannot remove the nut easily without causing damage to the threads of the u-bolt.
Note: Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.