RECIP BLADE 18T X 4in. BI-METAL CONTRACTOR 3/4in. WIDTH .035 THICKNESS - 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 PERCENT COBALT TEETH FUSED TO FLEXIBLE SHATTERPROOF BODY FOR RUGGED CUTTING. WHEN COMPARED TO STANDARD CARBON ALLOY BLADES. 1/2in. UNIVERSAL SHANK FITS ALL POPULAR RECIPROCATING SAWS. FERROUS/NON-FERROUS METAL OVER 18 GA. -1/8in. PVC AND FIBERGLASS.