Top Plate Size: Swivel: 5-1/4 X 7-1/4; Rigid: 5-1/4 X 7-1/4; Swivel (F): 4-1/2 X 6-1/4
Bolt Hole Pattern: Swivel: 3-3/8 X 5-1/4 SLOTTED TO 4-1/8 X 6-1/8; Rigid: 3-3/8 X 5-1/4 SLOTTED TO 4-1/8 X 6-1/8; Swivel (F): 2-7/16 X 4-15/16 SLOTTED TO 3-3/8 X 5-1/4