Height: 12″ Internal gas shock within a mechanical spring provides a wave-dampening soft ride. Andoized aluminum post with swivel. 3-1/2″ outer post with 2-7/8″ inner post. 9″ round anodized base. 4-keyed rotational locking collar covers the bushing to restrict movement. Allows 3-1/2″ of vertical travel. Display package. ABYC Class: (AD) H-31 Driver.