This drill bit is 12.5mm in diameter. The drill bit is used for the following kits: -Triton FP/RB (also requires 10.5mm drill bit) -Triton Ballpoint (also requires 10.5mm drill bit) -Atrax FP/RB (also requires 10.5mm drill bit) -Atrax Ballpoint (also requires 10.5mm drill bit) -Majestic Jr. FP/RB (also requires 10.5mm drill bit) -American Patriot FP/RB (only drill bit needed) -Electra (only drill bit needed)