I found the descriptions and pictures for these items a bit confusing and contradicted my understanding of the terms lowering and lowering. But maybe it's just me. What I was really looking for was just a countersink. You can't get a countersink here unless you also drill a through hole for what I would call the "shank" of a typical "old" screw. I say "old time" because I haven't used traditional single slotted pan head screws for many years. Along with other fasteners, I often use pan and round head self-tapping screws or other non-tapered screws. I already have several countersinks and drills. But why use them when you can make lead and drop at the same time? Drilling a through hole for a "bar" gives up the ability to screw the fastener into the material. I understand that when you attach 2 parts together you don't need threads in the first part, so having a through hole is desirable. But here you can't adjust the length of the shank part, so you may not get the bite you want with thin materials and small screws. The only adjustment is the length of the drill. Bit that sets the depth of the hole. The size of the #6 countersink I used seemed acceptable to me. You will see other sets that offer "tapered" bits. I also have a set of these but they tend to bend easily so I chose the ones with fixed bits. This set offers the added benefit of being able to "bury" the screw and then plug the hole. But if I had to buy again I would choose one of the other kits I see on this site that just have a basic countersink and pilot hole drill. The overall quality seems fine. just keep them