The HX.141-PK is a pack of four 9/64" Hex Adjustment Knobs that are designed for precise fingertip control of opto-mechanical components with hex socket adjustment screws in a compact system. The hex bit has a flat head on one end and a ball head on the other which can be accessed by loosening the setscrew in the knob and sliding the hex bit from one end to the other. The ball end hex provides angular flexibility and allows access to tight spaces.