The Standard size we used on our current jewelry items pictured is the MEDIUM Sized boxes.
Most pendants that were flat used small but we have since upgraded to use MEDIUM. The medium size works for flat items and 3D items.
Large size boxes are only availble in the RED print Sigil of Baphomet, that size will commodate all sizes including a ring up to size 13.
Medium size boxes also do the job but will fit a size 10 ring and smaller. Medium Size boxes are available in RED print and Gray print of the Sigil of Baphomet. Red print has the RED velvet interior and the Gray will have the BLACK velvet interior.