I have been using these JTJAOUEN countersinks for a month now, mainly oak, walnut, cherry and HDPE and they work very well. I have several sets of countersinks, but often I either don't want to drill as deep as needed to engage the countersink, or the drill bit is too big for the screw I'm using so they are separate. Sinkers were very useful. They are and stay sharp, the grooves are well formed, all ends are well centered and they make a nice round countersunk hole. They have finishing issues so I only gave them 4 stars but functionally they are great. I also like that they come in a box with styrofoam slots for each piece so they don't just knock on the drawer. I went ahead and drilled 2 holes in oak for this review. This is after using them for a month and 1 hole was with a pilot hole already in place and the other was just a countersink with no pre-drilled hole. You can see a small hex in the 3/8 and 1/2 countersink when there was a pilot hole, but it wasn't there when I first countersunk and then drilled. I definitely like this set of sinkers and would recommend them.