Gears are primary source of power transmission in a motion system. Avishkaar Robotronics design system offers different sizes of gears in high strength. The connecting holes are compatible with Avishkaar Robotronics square shaft design. Basic gears come is 3 different sizes of 12, 36 and 60 teeth. The pack also contains rack gear for conversion to linear motion. This pack contains these 4 types of gears in quantity of 4 each. Other gear pack and other movement design components are available separately. For more details please refer to www.avishkaarbox.com/movement.