Alternator pulley for Mazda Rotary 12A, 13B and 20B motors. Our pulleys are made from T-6061 billet aircraft aluminium, CNC machined, and finished in a black anodized finish. 76mm or 3" diameter. OEM specs. Lighter and stronger than stock. 15mm shaft. Dual sheave belt. Belts are not included. Made in the USA.