Platinum Series Pistons by Manley Professional engine builders and elite tuners around the world are running Manley pistons for some very good reasons. Constructed from durable, high quality 2618 alloy forgings. Features "Cam and Barrel" profiles that make big power, yet are friendly to the cylinder walls. Total seal piston rings are used exclusively. Unique (to Manley) fixturing allows skirt turning & ring groove machining to be performed in one single operation. This ensures the ultimate ring groove to skirt squareness. Features 2618 high strength material; Lightweight design .150" x 2.250" wall Premium Chrome Moly pin (Standard Series) included P/N 42251 9310 alloy .210" wall pin (Extreme Duty Series) included P/N 42551 Pressure balance groove Will accommodate +1mm valve sizes Premium Steel top rings with Napier seconds and round wire locks included PLEASE NOTE **The standard 86.00mm bore size pistons feature skirt diameters that correspond to the OEM Grade A or B bores, resulting in a piston to wall clearance range of .0023" - .0031". Check the bore grades on the top of your block and order the appropriate quantities of Grade A or B pistons. The grade A and B pistons are sold individually. Applications 2015+ Subaru WRX FA20 Specifications Rod Length - 5.090" Stroke - 86mm Comp Distance - 1.292" Dome Volume - -13cc Bore Size - 86.0mm to 86.50mm What's In The Box? 1 - Platinum Series Pistons Warranty Manley Performance Limited Warranty