Hot dip galvanized brackets with a top that swivels to let you set your bunk or bolster boards at the proper angle. Non-slip dimples ensure secure mounting on trailer frame. All are 2 1/2"W. Mounting holes: 2 1/2" on center. 9"L has 2 3/4" slots 11"L has 3 3/4" slots 13"L has 4 3/4" slots