Bird Perch End CapWorks greatly for 10mm diameter perchscan be resized to fit your needs

It has a 12,5mm internal diameter to fit with space, if you want to fix it better to dont rotate, you can glue inside, reduce size or place some filling material.

For larger or smaller diameters, I'd suggest resizing the pieceThe space for fitting in the bird cage, is for 3,8mm cages or smaller - as shown in reference size images

You can print any color you'd likeI'd suggest PETG, PLA or ABS

Feel free to use any settings you'd like

No support needed

For printing mine, I used 0.12mm layers;with 02 loopstemperature, speed, and etc, are all based on your printer preferences.infill 15% is good enough, but you can change it aswell