This axle is designed specifically for 72" wide I beam boat trailer frames. This 3500 lb Capacity Galvanized Boat Trailer Torsion Axle from Knott Axle is galvanized for corrosion resistance, and come with pre-installed with hot-dipped galvanized hubs and are common on many different brands of boat trailers. The "springless" suspension system uses four rubber chords surrounding the inner axle shaft to provide shock absorption at the appropriate levels based on the terrain and load spring, and will outlast traditional leaf spring suspension. Torsion Axles are mounted to the frame of boat trailers using U-bolts or bolts and can be affixed to I-Beam Frames, Tubing Frames, and C Channel frames. In most cases this axle would be used on an Aluminum I Beam Frame that previously had a torsion axle, and just needs a replacement.