Gives you longer system life without compromising weight Steel teeth last 4 times longer than aluminum Pound-for-pound, the strongest sprocket on the market The aluminum core is 70% lighter than steel Forging rivets into the sprockets provide exceptional strength Designed for bikes up to 1400cc in displacement Steel teeth last 4 times longer than aluminum Great for street, MX, off-road and ATV applications of all sizes. SPROCKET REAR STEEL 39T