I needed to replace 2 buttons on my Custom 24 with phase I winged tuners. They will fit ok but you need to press hard, the inserts are smaller than the original Phase I, so take your time as you could damage both the tuner & button! ; oil the insert of the buttons to help the tuner slide better. I finally made it by using a "C clamp".
These buttons look almost like the original Phase I.
Just one thing, the original Phase I buttons have a metal barrel inside the insert with the shape of the tuner and these new Phase III, dont,.
Also, the original phase I use 2 thin washers 1 metal & 1 plastic; the phase III buttons dont need washers as they have a little ring at the bottom for their purpose. hope this helps :)