The BMW 1.8L M40 / M42 pistons are developed for mild to high tuning, mainly for road or club race cars that want to develop their engine for high mileage and/or street use. Designed by ZRP engineers and manufactured in Germany from 4032 (T6) high-silicon, low-expansion alloy. This allows the engine builder to run a closer piston to bore clearance thus producing a better seal. This minimizes the slapping noise during cold start, common place among engines running forged pistons, providing a quite operation and low oil consumption. We have chosen a Full round skirt design with bottom reinforcing band, with oversize and deeper valve pockets to allow high lift camshaft profiles to be used. They have Offset pins for quiet operation and the wrist pins are made from 9310 alloy. Other features include Anti-detonation grooves to protect the first rings, gas pressure accumulator groove for better ring seal and vibration relieve. Premium Japanese quality 1.00mm x 1.20mm x 2.80mm ring package included. Product Features and Design Anti-detonation grooves for long wear life and performance Gas pressure accumulator groove in the 2nd ring land for longer wear life. Horizontal slots in the pin bore designed to allow oil to enter between the wrist-pin and pin-bore area. Precision CNC machined ring grooves 4032-T6 high-silicon / low-expansion alloy Honed pin bores Clip cuts on the edge of the Intake side Full Round skirt design with bottom reinforcing band for High HP/Boost applications Valve Pockets designed to allow over size valves and high lift camshafts Pistons designed to optimize squish for longer engine life and increased horsepower potential Optional coatings offered per request Thermal barrier coating “Blast Off Bronze"Moly Side-Skirt and Under-Crown coating “Stealth Black”