#41 13 Tooth 1/2" ROLLER CHAIN SPROCKET IDLER. Description: CHAIN SPROCKET IDLER CHAIN SIZE #40/41/420 TEETH COUNT 13 MAY COME IN SILVER OR BLACK FINISH. MAKE SURE YOUR CHAIN HAS THE SPECS BELOW : Chain # 41 Pitch 1/2 Roller diameter .306 Roller width 1/4 Pin diameter .141