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”x 3” square tube. The hole spacing center hole to center hole measures 3 5/8”. You will need to use a u-bolt 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. You will nearly always see this support bracket mounted with either Stainless Steel U-Bolt 1/2 inch x 3 inch x 4 5/16 inch or Galvanized U-Bolt 1/2 inch x 3 inch x 4 5/16 inch depending upon your desired level of corrosion protection. The perfect combination would be this Aluminum Bracket, mounted to an aluminum cross-member, with stainless steel U-Bolts. We have these available as an add on to this item.