Relatively easy to fit to the strap and very easy to fit to the guitar, I had no issues with the strap coming off as long as I used them.
There’s a metal clip that needs to be pushed in place to fit the attachment to your strap which is a little tough to do but far from impossible. I’d recommend keeping the locks on your strap permanently rather than remove them regularly.
I was able to fit these parts to my Gibson Les Paul without any need for filling or re-drilling holes, the screws fit the existing screw thread.
Keep in mind, these locks are nickel finish, so might not match perfectly with guitars that have chrome hardware (if that’s important to you).