Ideal for reducing diameter of round duct, sheet metal pipe, and downspouts for insertion into other pipes. Five blades make uniform crimps on sheet metal up to 20 gauge. Recommended for light or heavy piping -- furnace, smoke, wall stacks, air ducts, water heater vent pipes, and downspouts. Crimps up to 1-5/8" back from end for good overlap connection. Heat treated blades for longer wear, hardened pivot bolt for durability, and non-slip grips for comfort. For natural indraw on metal, always start with the three blades on top.