Springfield Marine Jon Boat Seat Clamp. Includes 360 degree ball bearing swivel. Swivel Specifications: 6 7/8" square; 4 hole pattern. E-coated steel to resist corrosion Features of Springfield Marine 1104010 Jon Boat Seat Clamp Quality durable construction 360 degree ball bearing swivel For Jon boats: 8" to 20-1/2" E-coated steel to resist corrosion Package Contents: Springfield Marine 1104010 Jon Boat Seat Clamp Springfield Marine 1104010: Jon Boat Seat Clamp