The largest dome in the range, formed to suit 127mm tube. Where the 76mm and 101mm domes cover surge pots and catch cans, this size is aimed at proper volume: dry sump oil tanks, larger swirl tanks and coolant headers that need to hold several litres without the tank becoming absurdly long. The pressed dome shape distributes internal pressure across the curve rather than concentrating it at a weld line, and the machined welding face makes for a straightforward, low-distortion TIG joint to the tube. Pair with matching weld-on bungs and fittings to build a tank exactly to the space you have available, rather than compromising around an off-the-shelf unit.