Absolutely love the D'Addario universal strap locks, I have a bunch of them. They're some of the lowest-profile strap locks on the market, they're extremely robust, and they look good too. Plus I've found they're very easy to install, and on most my guitars they were compatible with my existing strap button screws. Also, the replacement button still works with a strap without the lock attached if you're just swapping or trying other straps. Neat!

They seem to be relatively unknown because they aren't included in many reviews of comparisons even though they've been out for a few years. It's kind of surprising because at least to me, the D'Addario locks seem to take some of the best attributes of other strap locks and improve on them.