Ultra precise pinion gears machined to instrument quality standards. Constructed from light 6061 aluminum then hard teflon coated black. 8 additional "lightening" holes have been added to reduce the rotating mass, while the smaller pinions have a grooved back face to reduce their weight. No messing with the normal 0.050 allen wrench, these take the large 0.062 tip wrench that are used on your 5/40 socket set screws.