
I used a Powerbuilt 640931 ratchet with them and it worked great. At first I thought I wasted my money because of the bad reviews, but I gave it a try anyway. I assembled the wrong part of the Zen Desk I ordered and was unable to remove the three Allen screws. I turned the screws to get them out and I used the number four on the metric scale and they came out. The last one stuck badly but the trick is you twist it at an angle instead of straight and it came out. I'm glad I didn't have to spend a lot of money trying to find tools that would work.