This is an anti-theft lock screw--Security Knob and Key Knob Kit special for motorbike/ bicycle phone mount with double socket arms. It specially fits for ram phone mounts with long stem bases. Safety Function: it avoids your motorcycle/bike phone mount to be stolen outside. Easy Installation: just need to unscrew the original lock on the stem phone mount, and install it on. Just put the key away while leaving your bicycle phone mount outside. iMESTOU Anti-Theft Lock Security Knob and Key Knob Fit for RAM B Size Mounts or Other Motorcycle/Bike 1" Ball Double Socket Holder (2)