This square tube V-Bend aluminum cross-member is common on aluminum I Beam boat trailers. The tube measures 3 inches tall x 3 inches wide x 80 inches long. While this is considered an industry standard 80 inch cross member, it measures 79 1/2" tip to tip. The tubing has a 1/4 inch wall thickness. Boat trailer cross members are normally attached using U-bolts and bolts. If you have an aluminum framed boat trailer that has galvanized cross-members this is a great upgrade to switch the whole trailer to aluminum. 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.