If you use the the MAP or BVM I thinks it's more like 8mm but don't quote me on that. I run the large bvm hi flow clunk with the hi flow tank line followed by their hi flow tygon up to the UAT then the same from the UAT with a step down to the size of your pump input with a shutoff after the step down prior to the pump. Then the supplied fuel line from the pump to fuel filter into the turbine. BVM has a nice diagram on their website.