good quality HSS bits. You drill mild steel just right. They do NOT have jobber length as advertised. They just figured it out. See photo for comparison to REAL length of same diameter jobber. This wasn't a disadvantage for me as I use them to drill holes for tapping. As other reviewers have said, the smallest size pieces all arrived in a jumble and were a little hard to see. The smallest one was missing but I don't think it was worth returning as I probably won't be using it. The case is sufficient. The size isn't perfect when measured with a micrometer, but it's very close - close enough to be used to drill holes for tapping - better than fractional drills for this purpose.