Manley 04+ Subaru WRX STi (EJ257) STD Stroke 100mm +.5mm Bore 9.8:1 Dish Piston Set with Rings

These are high-performance forged pistons crafted from high-strength 2618 aluminum alloy. They are designed for superior high-temperature strength and fatigue resistance, making them ideal for demanding applications. Manley's unique "one fixturing" manufacturing method ensures perfect ring groove to skirt squareness for maximum horsepower. Each set includes tool steel wrist pins, moly skirt coatings (on select part numbers), and rings. The pistons feature "Contour forgings" for optimal strength-to-weight balance without grain interruption from internal milling. A multi-step top ring groove machining process ensures precise groove geometry, flatness, and finish. Other features include a pressure balance groove and precise pinhole machining for exact compression distance and lock ring groove spacing.