This pin lock knob can be added to any 1.5" diameter ball socket arm ("C" sized) in order to lock the arm and prevent it from being opened (see demonstration video below).

It consists of a 5/16"-18 female threaded security knob and key knob, and replaces all knobs on 1.5" diameter C size arms and mounts. It offers the ideal amount of leverage to properly tighten your mount to prevent slippage in heavy chop or in extreme vibration environments. With an emphasis on aesthetics and function, the RAP-S-KNOB5U low profile and only adds a small amount of additional bulk to your system when compared to the standard knob included. 

• Material: High Strength Composite

Note: The "U" in the part number reflects product packaged in poly bag.