This is a Stainless Steel 2 3/8 Round U-Bolt Kit that works great for boat trailers, especially in salt water. We offer this Leaf Spring U-Bolt Kit to mount your leaf springs and round axle together. This kit features (4) 1/2 x 2 3/8 x 5 3/8 round Stainless Steel U-Bolts with flat washers, lock washers, and nuts also in stainless steel. Also this kit includes Hot Dipped Galvanized 4 Hole plates to complete the kit. This kit would mount leaf springs to a 3500 lb , 2 3/8" diameter round trailer axle. These axles are common in both painted and galvanized steel. Having stainless steel u bolts will permanently prevent the issue of rusted hardware on your trailers axle.