The Starrett Bi-Metal Unique High Speed Steel Safe-Flex Hand Hacksaw Blade 300mm / 12" 24TPI 10UN. A patented solid state diffusion process produces the industry's most advance bi metal hacksaw blade. Massive increase in tooth strength and reduction in tooth breakage and fracture when compared against tradition bi metal blades. 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.