What size is a 5.5 mm crochet hook?
A 5.5 mm crochet hook is equivalent to a US I or 9 crochet hook, as well as a UK size 5.
What letter crochet hook is 5.5 mm?
It's a crochet hook with the letter I.
Is a 5.5 mm crochet hook a size 9 or I?
A 5.5 mm crochet hook is the same as a size 9 and a size I crochet hook.