Pro Tru sets include plasma moly 1/16, 1/16, 3/16 pre-gapped ring packages which provide excellent seal, friction reduction, and long life. Pro Tru pistons also come in a variety of volumes that allow the engine builder to choose the exact compression ratio required for their engine.Bore (in):3.425 in.Bore (mm):87.000mmPiston Style:Dish, with four valve reliefsPiston Material:Forged aluminumCompression Distance (in):1.130 in.Piston Head Volume (cc):+21.00ccWrist Pin Style:Press-fit or floatingPin Diameter (in):0.866 in.Gapless:NoFile Fit:YesTop Ring Thickness:1.0mmTop Ring Material:SteelTop Ring Facing Material:Gas nitridedSecond Ring Thickness:1.2mmSecond Ring Material:Cast ironSecond Ring Facing Material:Phosphate coatedOil Ring Thickness:2.8mmOil Ring Material:Stainless steelOil Ring Tension:StandardQuantity:Sold as a kit.Notes:Fits 4G63 engines, second generation 7-bolt with 100mm stroker crankshaft. Pistons include .225 in. wall tool steel pins.Part #K627M87AP