The Starrett Bi-Metal Unique High Speed Steel Safe-Flex Hand Hacksaw Blade 300mm / 12" 32TPI 2UN. These all purpose blades are an economical alternative when cutting mild steel, copper, brass, aluminium and other similar materials. Blades feature an all carbon construction with a hardened cutting edge and a flexible back. Excellent for interrupted cuts in cramped places or where the blade is subject to bending or twisting stresses. Starrett Hacksaw blades are available in bi-metal unique® high speed steel Safe-Flex® and Grey-Flex® High Carbon Steel.