The Sir Nickless protects armored cable wires by drawing the wires down, creating airspace above the wires and providing room for the cutter blade to shear through and sever the armored casing without nicking the wires within. The Sir Nickless is unique in that it has a curved design that allows the wires to draw down providing room for the cutting blade. The cable Cutter works well on all popular types of armored cable up to 3/8 inch diameter. IDEAL® Sir Nickless™ Replacement Blade, Blue Sapphire