HEAD & BASE GASKET SETS. In addition to the ProX Complete and Top-End gasket sets a new assembly is set-up, the ProX Head & Base gasket sets. Where the Top-End gasket set contains all components for a complete piston rebuild the new ProX Head & Base gasket sets just contain 1 head gasket and 1 base gasket. This results in a more cost efficient kit when not all components are being replaced. The Head & Base gaskets are made of all premium base materials. Each gasket is precision cut for optimal fit and prefect seal. A full range of Dirtbike Head & Base gasket is available. ProX Head & Base Gasket Features :. Manufactured of all premium base materials. Precision cut for optimal fit and perfect seal. Cost efficient assembly. Full range of Dirtbike sets available.