SeaSport 2 7/8" Products are Built to Handle the Big Water Heavy duty 2-7/8" posts and 9" diameter machined bases are engineered for strength and safety in harsh off-shore conditions Type A/Operator Models lead the industry with these features: Ergonomic positive-locking handles with stainless steel components PowerLock Multi-Action handle controls both swiveling and height adjustment. No more wondering which handle does what TwinGlide Bushing ensures smooth operation and maximum stability at t any height position EZ-Lock CAM-Action makes seat removal simple. When engaged, seat mount is posi-locked to the post and swivels freely