Men’s ring size ???

Okay so for Christmas my boyfriend mentioned awhile ago he’d like one of those silicone rings (that are normally for wedding rings.) However since this is a Christmas present I want it to be a surprise however I don’t know his ring size. So I was wondering what is a typical men’s ring size? Granted even if it’s not his exact size the ring is again silicone so would still decently fit. I just however need a ballpark range.