Gold or silver rings can be sized down (or up) 2 sizes, stainless steel rings can only resized 1 half of a size. Platinum rings cannot be resized.
How Many Sizes Can A Ring Be Sized Down? Definitive guide
How many sizes can I resize my antique engagement ring by? – The Vintage Ring Company
How Many Sizes Can A Ring Be Sized Down? Definitive guide
Ring Size Chart
How Many Sizes Can a Ring Be Resized?
How Many Sizes Can A Ring Be Sized Down? Definitive guide
How Many Sizes Can a Ring Be Resized?
How Many Sizes Can a Ring Be Resized?
Ring Sizing 101: Everything You Need to Know – Noe's Jewelry