Tie Down Engineering Galvanized Steel Panel Bracket 

"One piece, heavy-duty, hot dipped galvanized 11 gauge steel. Specifically designed to support keel rollers. Slots accept 7/16" or 1/2" diameter bolts and provide vertical adjustment. Roller shaft diameter can be 1/2" or 5/8". Bracket is 4-3/8" W. Roller size is 4"."

Width Between Slots: 2", Roller Size: 4", Bracket: 4-3/8" W"