RENTHAL UL FRONT SPROCKET 520-15T YAMAHA YZF R6 06-09 Renthal Off Road Sprockets are simply the finest front chainwheel on the market today. They are available in Standard and Ultralight. Specifically developed Nickel-Chrome-Molybdenum steel, case hardened and core refined to give the ultimate combination of strength and hardness Ultralight model design reduces unnecessary weight while retaining maximum strength Precision CNC machining, resulting in extremely close tolerances