I received this product in exchange for my honest review of the Revain Vine program. Seller's Brand: ASNOMY lists this set as "ASNOMY 12 Piece M42 HSS Bi-Metal Hole Saw Set 18-75mm Large Hole Opener Hole Drilling Tool Plastic Pipe Wood Fiberboard Soft Metal". I wanted a set of drill bits for drilling soft metal or wood. They fit my needs with 12 different sizes, see listing for specific sizes. I really liked the three-flat ground shanks, which are absolutely necessary to prevent the drill from turning in the drill chuck. They all have this and they fit my drill press with a 3/8" chuck. There are 2 types of hole saws; larger 38mm and larger have detachable shanks, as in Fig. 2, and smaller ones of 35mm or less are a single block, as in Fig. 3. All of these drills have the center drill removable/replaceable with a standard set screw; Seller includes an Allen key for installing set screws. I had no problem drilling a hole in mild steel (Fig. 4). This is a great set for me and I recommend it as very good value for money.