This is the optional 15 tooth clutch bell for the Losi 8IGHT buggy. The clutch bell sits over the clutch shoes, and will be engaged when the engine rpm's increase. It will allow the engines power to pass to the center spur gear and the rest of the drive train. The smaller the clutch bell, the more bottom end acceleration the buggy will have, but with less top end speed. A clutch bell with more teeth with increase top end for those that are looking for a higher top speed, but will reduce bottom end acceleration.