This is an Aluminum Cross Member for boat trailers. It is made out of 3 inch x 3 inch x 1/4 inch thick aluminum square tube. This Cross-member has a V-Bend in the middle of it which gives it a 3 inch dip. The cross-member measures 58 1/2 inches long. It's normally attached using bolts or u-bolts to aluminum I-Beam boat trailer frames. This cross member is perfect for replacing rusted out galvanized beams, or if you just want to have an extra cross member to attach bunk brackets to. For Mounting U-Bolts or Bolts go to Boat Trailer Bolts or Boat Trailer U-Bolts. The Stainless Steel U-Bolt 1/2 inch x 3 inch x 4 5/16 inch is typically the go to U-Bolt for mounting this product to your I-Beam frame. If you had previously had your Galvanized U-Bolts eat through your cross-member, using this Stainless Steel one will prevent this issue from happening again. This component has a 3" drop that is specifically intended to prevent impact from the V-Hull on your boat when loading and unloading at the ramp. This component is extremely important on your boat trailer as it is responsible for supporting the weight of your boat, and keeping the frame square.