This is the locking nut neck mounting screw for Schaller/ Floyd Rose locknuts. It uses a 3.0mm Allen key to tighten. 

Length: 0.0000 in
Width: 0.0000 in
Height: 0.0000 in
Weight: 0.200 oz
Packaging: 0.0000 kg
Units in box: 1
Parts by Make/Model > Floyd Rose Tremolo Parts > Floyd Rose Locking Nuts
Parts by Type > Mounting Hardware