My dad has a fan (The one in the title) and he didn't have a knob for it and was turning the small switch to turn it on. So I made him this to use instead. It prints snug so if need be print it at 101-102% if you are having issues. This was designed by me after taking inspiration from 1950-era radio knobs and car wheels. The inner opening has dimensions of 5.6mmx6.6mm