One is required per piston, eight are required per car.
About Prestige Parts Piston Rings:
Quality control is a significant factor in the manufacture of highly stressed components such as piston rings and the rings are manufactured under an ISO/TS16949 quality management systems using modern in-process techniques such as poka-yoke (manufacturing techniques to error-proof the finished component). The latest optical and laser technologies with tangential tension testing ensure every ring produced meets our exacting standards of material and dimensional accuracy.
Tighter dimensional tolerances, better surface finish, smaller draft angles, and near net shape castings are produced from the on-site grey and ductile iron foundry reducing machining therefore producing a cost effective but high quality ring. Coatings chosen to suit each ring and application provide the correct level of wear resistance, anti-scuffing, low friction and rust prevention as appropriate.