Sets of 4 large polythene gears with diameters of approx. 15mm, 22mm, 32mm and 40mm. (Tooth count 12, 20, 30 and 40.) All 6mm thick. Small gear is a press fit onto our electric motors. Large gear clips to the end of a cotton reel (if required). Use 3mm axle. Available in red, yellow, blue and green. Each pack contains 20 sprues with 4 gears on each.