These are the lower / leading spark plugs for the Mazda RX-7 Rotary Engine 13B.
Safe for Stock port / Street ported motors.
NGK V-Power spark plugs are commonly used in many high performance engines. These are the only spark plugs with the V-Groove technology. By reducing the surface area of the nickel electrode tip closest to the ground strap, ignitability is improved while spark voltage requirements are reduced.