Cut in 3 equal strips. For a regular toilet paper roll, 1.2 inches works well. If you cut them too small, it can be fixed as long as they’re all the same size.
Pinch the three pieces together and tape at both ends from the outside. Slide into the tube, and your done. Kaleidoscopes usually have an attachment at the end full of stuff, but I wanted to be able to use this as an attachment to my camera lens for a kaleidoscope effect.
Decorate the outside of the tube with sharpies/ more mirrors. I wrapped a strip of the mirror around it.
If you want to create a more traditional kaleidoscope, try attaching a bag full of leaves or beads onto the end with a rubber band.