Hard anodising (HA) is a surface coating which greatly improves the hardness and wear resistance of the rear sprocket. Triumph Renthal rear sprockets are precision CNC machined using 7075 T6 grade aluminium alloy. Then Renthal apply the hard wearing finish for greater mileage. Triumph Renthal rear sprockets are about 1/3rd the weight of standard steel rear sprockets. This will reduce unsprung weight and rotating mass.