For cutting flexible fiberglass wool duct and duct board. Double edge blades are ideal for blind cuts in flex duct. Ergonomic cushion grip features one serrated cutting edge and comes with a puncture-resistant nylon sheath. Resharpenable, heavy-duty cutlery grade steel blades. Malco® Duct Knife, Resharpenable, 6 in L Bit, Steel Bit, Gray, 13.5 in L x 4.8 in W x 1.3 in H