The 9313 0.5 inch (12.7 mm) Adjustment Screw provides smooth, wobble-free adjustment combined with exceptional long-term stability and low susceptibility to thermal variation. It is the same 1/4-80 precision screw used in our optic mounts and allows you to build your own mounts or positioners. In addition to a travel of 0.5 inch (12.7 mm); the screw has a ball tip, unbraked brass bushing, and is knob adjusted.