diamond center 6.0 ->7.0 mm
4.5 -> 5.4 https://www.cgtrader.com/3d-print-models/jewelry/rings/engagement-ring-simple-95a88ccd-121c-4520-b252-86b70f168828
5.4 -> 6.0 https://www.cgtrader.com/3d-print-models/jewelry/rings/engagement-ring-simple-54
7.0 -> 8.1 https://www.cgtrader.com/3d-print-models/jewelry/rings/enggagement-ring-simple-70