I purchased these to fit to a PRS SE Custom 24, which has a tremolo, and no locking heads, and therefore some tuning instability.
These installed into the original headstock holes perfectly - no drilling required. Took me 30 minutes and I'm no expert.
Stringing the guitar is now really easy, though the included instruction are unclear on how to actually do it. Simply line up the hole with the fingerboard, thread the string straight through, and turn the tuning key until it locks. Simple, when you know how!
The guitar now holds its tuning perfectly. It really is much, much better. These are highly recommended. They also look great on this specific guitar - they are spot on.