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: 2.5mm x 0.45, 3.0mm x 0.50, 3.5mm x 0.60, 4.0mm x 0.70, 5.0mm x 0.80, 6.0mm x 1.00, 8.0mm x 1.25, 10.0mm x 1.50, 12.0mm x 1.75), (Dill Sizes: 2.05mm, 2.50mm, 2.90mm, 3.30mm, 4.20mm, 5.00mm, 6.70mm, 8.50mm, 10.20mm). Picture Shown: NC Tap Drill Set.