I use those on a lot of my guitars, and recommend them to people when I do set ups for them if they don't already have some sort of strap lock system. I really like these because I can use the same strap on many guitars, and they are silent unlike the Schaller's.I rarely use a strap anymore unless I wander out wireless in back yard, but these Diaddario elliptical buttons keep your guitar from falling off without the need for a giant strap hole or a saucer on your guitar.
Dang, those are huge. Do they tend to slip on the slot any?