Cockpit table extension fits to an existing game chair post (600mm) raising the height of the post 150mm (750mm table height). A flared section with 2 stainless locking handles fits over existing chair post 75mm, 76mm or 88mmn O.D tubing. Reelax helm and passenger seat swivel casting (RX12) is full nylon bushed which means there is nil metal to metal contact between swivel and tube. It is a robust pressure die cast marine grade alloy component which is powder coated black. Comes with a marine grade stainless steel locking handle to lock the swivel. Can be adapted with a fore and aft slide (see 2.6a) Please specify the outside diameter (o.d) of tube to fit. 75mm - 76.02mm - 88mm