Professional 2.5mm Wall Tactical .625 Cal Muzzle Guard Peep Sight By Venom Blowguns&trade; Compatible with Cold Steel Professional&trade; and Venom Blowguns&trade; 2.5mm Wall Blowguns FOR 2.5MM WALL BLOWGUNS Slides onto .625 PROFESSIONAL 2.5mm Wall Blowguns, will not fit Smaller MAGNUM 1.5mm Wall Tubes IF YOUR TUBE IS THE SIZE OF A PENNY YOU HAVE A 1.5MM WALL BLOWGUN IF YOUR TUBE IS THE SIZE OF A NICKEL YOU HAVE A 2.5MM WALL BLOWGUN THIS WILL NOT FIT SMALLE MAGNUM MODELS, Please Email Us if you have any questions