Yaroslav
This ring has sizes 4 to 11 USA. If I'm not mistaken, 18 rim (Brazil) corresponds to size 7 1/4 US. Size 7 US is present here, it should fit you.
Sizes us 4-11
Metal weight size 5:
Gems:
Side band size 5:
Gold 14kt - 2.5gr
1mm - 52
1.2mm - 38
It is not a perfect copy of Tiffany ring, there are changes in it.
Model is ready for prototyping on CNC and 3D Printing.