This heavy duty Aluminum hat bracket is a perfect replacement for aluminum boat trailers. It is made out of aluminum that is 3/8” thick at the mounting surface and a 1/4" thick on the bottom plate. It can be used in conjunction with a V-guide set up or bunk board supports. Typically this item will fit on a trailers cross member that is 3”x3” square tube. The hole spacing center hole to center hole measures 3 5/8”. You will need to use a ubolt that is 1/2" diameter and 3" wide on the inside. This hat bracket is used to clamp front v-guides or bunk boards that use 2" x 2" square tubing for their support.