This is a bowden cable driver made for SG90 servos. The frame of it is the format of a standard servo. It drives the cable 1cm over a 90 degree throw. Its designed to use hollow 1/8" upholstery bead as bowden sheath. I used fish line as the cable, use what you like :]

The cable traps via a loop in the pulley. 

This works with the bowden cylinder I also have posted on printables.com

This is just two parts, the frame, and the pulley. Its designed to work with the screws that come with the SG90 servo.