A.T.O.M. Exosuit

The A.T.O.M. Exosuit is an exosuit designed by Ray Palmer which is first shown and named near the end of Draw Back Your Bow. It is unclear what the 4-letter acronym stands for or what it does. Ray calls up the designs after inquiring about a dwarf star alloy which may be related to the suit.

Trivia
In the comics, Palmer was a hero called "the Atom" who had a suit that allowed him to shrink.