Motors intended to be used with planetary gearheads; assembly of the two is quick and easy, requiring no special tools Motors can be used with GP42 42mm gearheads e.g. (stock no. 420-5041) using fitting kit (stock no. 468-4775) Speed Constant: 581rpm/V (stock no. 468-4797); 317rpm/V (stock no. 468-4804)