2.5mm Wall Tactical .625 Cal Muzzle Guard Peep Sight, Hand Grip and Tactical Mounting Rail By Venom Blowguns&trade; Compatible with Cold Steel Professional&trade; and Venom Blowguns&trade; 2.5mm Wall Blowguns Tactical PEEP SIGHT, HAND GRIP And MOUNTING RAIL FOR 2.5MM WALL BLOWGUNS Slides onto .625 PROFESSIONAL 2.5mm Wall Blowguns, will not fit 1.5mm MAGNUM Models 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 Please be careful in your sizing and best to order only if you have your blowgun in front of you to check sizing