Drilling stainless steel (SS) or tough cast iron requires a quality drill bit. Using a good quality drill bit makes my DeWalt Drill power tool much more efficient. These are high quality M42 8% Co HSS drill bits (2 equal sizes) and are supplied in a plastic carrying case. (Figure 3). If I want to drill stainless steel (SS) this is the bit I want to have and use. These quality tips make it much easier for me to implement DIY projects. They are sharp and when used with a quality cutting oil like Evo Dyne Cutting Fluid makes it easier to drill through stainless steel and other carbides. Chuck so big should have this feature. The bit size is marked on the shank. TIP: When drilling SS, use low RPM (500) and lubricate for best results. The cutting fluid reduces friction and heat build-up by allowing the drill bit to cut into the metal without being "welded" by the red heat. A small starting hole is best when I need to drill a large hole, so this size is great to have on hand. The step drill bit (picture 2) helps with centering and I recommend drilling a small starting hole first as they are 3/8" (9.5mm) drill bits. Very helpful! I recommend these branded M42 metric drill bits STROTON with 8% Cobalt for Stainless Steel and Carbide (9.5mm x 2 pack) Excellent cobalt drill bits at a good price I hope you found the information and my review useful.