IRWIN IRW10507580 Pro Snap-Off Screw Knife 18mm The IRWIN Pro Snap-Off Screw Knife features a bi-metal blade. A performance knife featuring a manual screw for locking the blade in the required position, a stainless steel blade guide, cartridge for storing 2 blades, hinged end-cap, slim nose and textured grip. In addition, the screw fixture allows for convenient user control blade fixing. Size: 18mm