Garelick Adjustable Height Seat Bases - Smooth FinishFeatures: Seat raises or lowers, locks at desired height; 4 prong spider swivels 360 and locks; Available anodized finish which helps prevent saltwater corrosion and weathering; 2 7/8" (7cm) diameter smooth stanchion tube, 9.25" (23cm) diameter base plate; Specifications: 75035: Polished 12" - 17" (30 - 43cm) High ; 75235: Anodized 12" - 17" (30 - 43cm) High; InstructionsMounting Instructions