This ring is a parametric design and is available any size-
The ring on this page is a 18.90 mm inner diameter size
equivalent to :
size 8 3/4 in USA /
size 19in / Netherlands, Switzerland Spain and China/
size R-1/2 in /UK, Australia and Surafrica/
If you need any aditional sizes, please let me know, same price
www.bioplastic3d.es