Water pump mechanical seal and bearing. No mods of any kind are required to use this kit and piston runs on pump or race gas. We recommend that this be installed by a qualified mechanic with experience doing this type of work. Piston comes with specific instructions for setting ring gap.Failure to follow these exactly will result in motor failure. The item "Raptor 660 Cases Bottom End Complete Rebuilt Motor Engine Rebuild Kit Big Bore" is in sale since Monday, June 8, 2020. This item is in the category "eBay Motors\Parts & Accessories\ATV, Side-by-Side & UTV Parts & Accessories\Engines & Components". The seller is "bpracingatv" and is located in Upland, California. This item can be shipped worldwide.