I used a set on my PCR Pro, AND a good set of drivers and had no problems at all with them. On the other hand I used a set of USSF screws on my maxx, with the same drivers, these are by far the crappiest screws I have ever used. Talk about a sloppy fit, metric wouldnt fit right, standard, nope, avoid these at all cost!
I got a set and after using the first 4-5 called them up for a refund. They wouldn't give me one so I tossed them in the rash along with ever doing business with them again. SLOPPY fit..