Contractor Series Cobalt Bi-Metal Reciprocating Saw Blades. Lasts 10X Longer. Unique Nitro Hardening Process For Optimal Strength And Blade Life. Fused Cobalt Teeth. 5% Cobalt Teeth Fused To Flexible, Shatterproof Body For Rugged Cutting. When Compared To Standard Carbon Alloy Blades. 1/2″ Universal Shank Fits All Popular Reciprocating Saws. Ferrous/Non-Ferrous Metals, Nail Embedded Wood, Composite, And Plastic.