The RAP-S-KNOB3U consists of a 1/4"-20 female threaded security knob & matching key & replaces all knobs on 1" diameter B size arms & mounts. The RAP-S-KNOB3U 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 & function, the RAP-S-KNOB3U is low in profile & only adds a small amount of additional bulk to your system when compared to the standard knob included. At a fraction of the cost of currently available keyed locking knobs, the additional peace of mind & tamper resistance comes at a very affordable price. The RAP-S-KNOB3U is the perfect accessory for keeping your mounted electronic device safe from theft & tampering.