This is a gripper. This is a Tower-pro SG90 made only. SG90 is inexpensive small servo motor. About $ 3. SG90 is a friend of 9g servo.
This Please be used in conjunction with the servo motor holder. http://www.thingiverse.com/thing:746116 http://www.thingiverse.com/thing:714174
I will connect each part in M2 × 12mm bolts and nuts. Please adjust the meshing of gears with a file.