Red rubber surface with 1 side teeth belt.
30-3M-2640 is 40mm spring diameter; 30mm wide and 2640mm long
43-3M-2640 is for 80mm to 120mm height springs; 43mm wide and 2640mm long
58-3M-2640 is for 130mm to 230mm height springs; 58mm wide and 2640mm long