The expression is "fits someone to a T". It means it is a perfect match for that person. "The description of the suspect fits him to a T." (He looks exactly like the description) "That dress fits you to a T." (That dress is perfect for you in particular. Does NIT refer only to dize) "You have all the requirements for the job. The position would fit you to a T"

you can also say, "fit like a glove"

I don't know what it means.