Included in the company's mid-range 6600 hardware series. The cushion is contoured to resemble an old-fashioned motorcycle seat and is 70mm deep, though quite firm. Height is adjustable telescopically, keeping the weight down, from 44 to 69cm.
The cushion has a snug-fitting socket which the hollow tube locates into underneath. It is possible that regular use will misshape the tube to the degree that inserting and/or retrieving it from the socket could prove a little problematic.