This listing is for a set of (4) Sealed Power cast pistons and a cast piston ring set (Hastings/Perfect Circle/MAHLE) in your choice of sizes compatible replacements for for Mercruiser 2.5L 120hp applications using the Chevrolet 153ci 2.5L 4-cylinder engine. P/N (4) 235NP & 50452CP Piston specifications are as follows: BORE: 3.875" (at STD) HEAD TYPE: Flat top with valve reliefs RING LANDS: 5/64"-5/64"-3/16" COMP. DISTANCE: 1.780" PIN DIAMETER: .9275"