"it fits perfectly" is correct and usable in written English. You can use it when you are referring to something that matches or works well with something else. For example: "I found a dress that matched my shoes perfectly – it fits perfectly!".
Personally, I liked the bedroom dock because of its size and practicality; it fits perfectly on a bedside table.
It's true that the surname Maddux lends an alliterative lilt to the nickname, but it fits perfectly for its opposite implications.
"It fits perfectly".
It fits perfectly in the hand".
"It fits perfectly with everything we're trying to do here".
"It fits perfectly with the plan," Mr. Milliner said.
It's really light, and it has wheels and it fits perfectly in the overhead".
Thanks to Ludwig my first paper got accepted! The editor wrote me that my manuscript was well-written
Listya Utami K.
PhD Student in Biology, Bandung Institute of Technology, Indonesia