I bought these a little ways back. I finally had an opportunity to install them on my guitar. I got one on no problem. I then started to install the second one, but when I started tightening the screw (just finger tightening with very little pressure at this point) it flat out broke. I had barely gotten any of the screw through and the corner broke off! Perhaps that one was just defective seeing as I did manage to get another one on without much trouble ... I don't think I'd buy these again though ...

these things are life savers. i used to break strings all of the time, but after i put these in i never break strings. seriously, i haven't broken a string in over 6 months, and i play hard and for at least an hour every day. i'm putting these on all of my guitars.