These were on sale half price, when I got them they were open and the screws and lock washers were missing.  Someone apparently had installed the buttons on their guitars then sent back the locks.  I sent them back and got a quick refund then bought some Fender Strap Blocks.  They are just rubber washers that stretch to fit over the strap holder behind the strap.  Much cheaper and fit any guitar without having to drill and install new strap buttons, and they work great.  Save your money.