238 Series Socket Bases -Stainless Steel 7 inch x 7 inch Square, Centered Hole, ABYC Code – AO, Req. Dia. Mounting Hole – 3 inchF. 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 hard-anodized aluminum All springs are stainless steel Bases are bead-blasted 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.