This trailer leaf spring U-Bolt kit is designed to be used with a 1 3/4" round axle. This U-bolt kit includes four zinc plated 3/8" diameter u bolts that are 1 3/4" wide inside and 4 3/8" long. Also included in this kit are two Zinc plated mounting plates with eight zinc plated nuts and lock washers. This U Bolt mounting kit typically would be seen on a 1400 lb to 2,000 lb trailer axle. Zinc Plating increases the corrosion protection and pro longs the life of your axle mounting hardware.