These fit a Philips screw. It is best to use flat headed screws and embed them deeply. Then the caps fit on very well. I wish they were a little more opaque white…they ARE white, and they are not see through exactly, but a whiter look would have been better on my white shelves. I feel that I can still see the screw head a bit through the cap…especially when I had to use a black screw in one instance. Also, the edges around the caps are a little rough. That being said, they still did the job for me.