Board Thread:Naruto Discussions/@comment-4682609-20140507083715/@comment-1512913-20140514184144

"There is still a good chance that with narutos jutsu, kakashi can still use the sharingan just hasn't activated it yet" Naruto restored Kakashi's own eye, the Sharingan wasn't a part of Kakashi, there is no way for Naruto to recreate it.

"I think that Naruto returned the same eye to him, it was said to give back what he had. It cant be the eye from when he was a kid cause it would be too small and would not even fit in his head. I think the Mangekyo eye was returned to him or reformed by Naruto"

The eye's size is fully grown by puberty and doesn't get larger beyond that point I believe.