Need to replace that bottom head gasket? Whether your current gasket wears down over time or you’re swapping out your old cylinder body, you’re likely going to need a new 100cc Bottom Head Gasket. The bottom head gasket is positioned between your engine’s cylinder body and crankcase. As such, it provides a tight seal between both parts. With a 100cc Bottom Head Gasket, you’ll be able to ensure proper pressure and combustion every time you ride.