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 INCH UNIVERSAL SHANK FITS ALL POPULAR U.S.A. RECIPROCATING SAWS. FERROUS/NON-FERROUS METAL OVER 1/8 INCH . S/S TUBE, PVC, CAST PIPE, AND NAIL EMBEDDED WOOD.