It is made with 3 gears、 can vividly demonstrate deceleration level between gears. Turn any gear、 other gears will follow in rotation、 reduction ratio among the 3 gears is 9:16:24、 can be a perfect interesting teaching material for teaching mathematical proportion formula. Dimensions: 6.69 in x 2.05 in x 0.55 in (17.0 cm x 5.2 cm x 1.4 cm) Weight: 0.49 oz (14 g)