This is an add-on for your Pokemon Go Plus that you can use to wear it like a ring. I like wearing it on the inside of my hand for easy access to the button on the Go Plus while I'm walking. The interior diameter of the ring is 20mm.
I printed it upright like the file shows, and the scaffolding was very easy to remove. If you can't do rafts, it's probably fine, but I wanted to make sure it stayed very straight. I printed this in ABS.
Wearing it on the inside of my hand