HSS for added wear resistance & better lubricity of tool surface which increases tool life & productivity. 18 piece set in metal index. Includes the following tap sizes with their corresponding tap drill: (Tap Sizes: 6 - 40, 8 - 36, 10 - 24, 10 - 32, 1/4" - 28, 5/16" - 24, 3/8" - 24, 7/16" - 20, 1/2" - 20), (Dill Sizes: #33, #29, #25, #21, #3, I, Q, 25/64", 29/64")
