VertexWinderosa Piston Kit Fits Husqvarna, Fits KTMWe wanted a lightweight cast piston that would outlast the OEM and aftermarket forget pistons. The fact that we cast our content to an unprecedented 18 21% which gives our Vertex pistons a fantastic life span compared to other pistons on the market. Pro Circuit has been testing and using these piston kits with great results. So if price, look no further Vertex, the choice of champions! Cast aluminium alloy (not forged) with a 18 21% silicone content