3 versions for 7.8mm, 5mm and 1/4"=6.35mm prop shafts.

I've tested a bunch of APC props 4.75" to 5.25", APC 4.75x5.5E is the fastest prop yet and the acceleration, climb and flight time is still good.
This battery pack is my favorite, fits with no mods Tattu 450mAh 2S 7.4V 75C Lipo Battery Pack with JST-SYP plug

To swap the adapters remove the motor cover and take out the 2 small screws. Pull the motor wires out of the foam so there is some slack. Work the motor out and then twist the stock prop adapter back and forth until it comes off. Twist on the new prop saver, it should be hard to twist on. Keep twisting it back and forth until the prop saver is touching the motor. MOUNT THE MOTOR BEFORE PUTTING IN THE PROP SAVER SCREWS. The prop saver screws are 2mm outside diameter, ~6mm long servo mounting screws. Screw them in the same on each side to keep them balanced, I use the blade of a small screwdriver as a depth gauge.

Print with the BALL UP 100% infill.

I now print these in PETG, it's a little stronger. Settings same as below except higher temps.
Ender 3S1, Geeetech Silk silver PLA, infill: 100% gyroid , supports, 0.2mm layer height, adaptive layers, build plate adhesion: skirt Z Seam alignment: random (otherwise prop saver may be slightly off center)