What size is a 7 mm crochet hook?
The 7 mm crochet hook refers to the measurement in millimetre. There is no US equivalent, however it's the same as a UK size 2.
What letter is a 7 mm crochet hook?
There is no letter equivalent to the 7 mm crochet hook. The closest letter size is the K, which is a 6.5 mm crochet hook.