IVY Classic 28212 B410P 4-Inch 10 TPI Metal/Wood Cutting T-Shank Jig Saw Blade, Bi-Metal, USA, 5-Pack For metal/fine wood cutting, Cobalt Advantedge (Registered Trademark) Bi-Metal with 8% cobalt matrix II alloy-steel cutting edge retains hardness Cutting edge electron welded to flexible, alloy-steel back for consistent quality Precision milled shatterproof teeth with Rockwell Hardness of 65-67 HRC. Made in USA, 10 TPI, 4-inch length x 3/8-inch width x .035-inch thickness