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. Wood, PVC, Plastic, Composite, And Nail Embedded Wood.