Big wheel for cats. They can run inside so they loose energy and become more relaxed.
It is not prepared for direct print yet. It's so big so it has to be cut and glued / bolted. A bug in OpenSCAD causes final model to have little space for small wheels.
Tutorial for customization:
1) set inner diameter "d" and width "w"
2) set "runWheel" - size of small wheels which should be bought (inline skate wheels)
3) set parameters of bolt and nut (also to be bought)