Premium-quality hypereutectic aluminum alloy pistons are used on most production LS engines (the LS9 supercharged uses forged aluminum).They are lightweight, durable and promote quieter operation. Chevrolet Performance offers production and oversized Pistons for many applications. They're sold individually, unless otherwise specified. 89017777 4.125" +.020" 1.2, 1.2, 2.0mm Oversize LS7 ring pack.