Makes precise holes in duct board for flex duct take-offs. Supplied with standard double point utility knife blade for cutting 1 inboard. Use special no. KBHC blade for 1-1/2 in(38.1 mm) duct board. Cuts 4 to 20 in (102 to 508 mm) diameter holes in fiberglass duct board. Operation is fast and easy. Cutter rotates counter clockwise on a center pivot punch. Durable extruded aluminum frame and engineering grade molded plastic and nylon components. Blade holder stores in body for safety and to protect blade from damage when not in use.