Made for my cat. I used hot melt glue to stick them under the shoebox, and the cat can now roll around. I used a 2mm TIG welding rod as the axle, but I'll try to make a version using a 1.75mm wire as the axle. I might need to use a drill to smooth out the inner holes of the wheels and the brackets.

The wheels are small, but they can withstand some weight very well. They can also be used in other applications.