238 Series 2-3/8 inch Fixed Height and Pro-Pole Extension Posts . Bulk-Pro-Pole Extension Posts - Type inchB inch (Height Measured From Deck to Top of Seat Mount)-Pro-Pole Extension Post, 27 inch Height, ABYC Code. The Seat Mount has Rock-Solid Slider Movement and Silk-Smooth SwivelHas strength, style, and corrosion-resistance to the core, Corrosion-Resistance. Pedestal tubes are made of hard-anodized aluminum. All springs are bead-blasted (to close aluminum porosity) and clear-coatedSmooth Movement Without Wobble Slider has gear-tooth lock mechanism; locks solidly, disengages easily Slider rides smoothly on acetal linear bearings. Clean Style, Ergonomic Design Styling is clean and uncomplicated Handles are ergonomically designed to be easy on the hands and easy to reach.