S3 Head InsertIt uses the best alloys available , to obtain a better output & more traction. The advantage of these heads is that they can hold more water and have thicker walls which helps with the cooling rate, thus improving slightly low revs power. STARS HEAD kits eliminate the hot spots typically found on cast heads. Forged in the best aluminum alloy to obtain a top quality component and high durability. Its new design has thicker walls and higher water flow