This is the TTC Bulkhead Chair Mount only, which may be used with many styles of seat. The stanchion is 2 7/8" diameter. The mount features heavy duty construction from structural grade aluminum. The mounting arm is made from an eight inch deep aluminum I-beam, 20" long. The bulkhead bracket is constructed from a section of 1/2" aluminum flat bar with six pre-drilled holes for the mounting bolts (not included). The mounting arm may swing up to 180 degrees, freeing up valuable deck space or may be held in position with a locking pin.