Fixed Height Extension Posts (Height Measured From Deck to Top of Seat Mount)238 Series has Strength, Style and Corrosion-Resistance to the Core: Pedestal tubes are hard-anodized aluminum All springs are stainless steel Bases 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 bearingsClean Style, Ergonomic Design Styling is clean and uncomplicated Handles are ergonomically designed to be easy on the hands and easy to reach