Motorcycle tire and wheel ear plug/tunnel.
For your size, just message me, and I can make it that size and put it for sale.
Note that stainless steel will not show nearly as much detail as silver.
Only want 1 side? Get it here:
https://www.shapeways.com/product/ZYG2VBEEZ/dirbike-wheel-earing-plug-10mm-00g-single