As revealed Saturday in the Comic-Con International trailer for Season 5, The Flash will at long last introduce the iconic costume ring to Barry Allen's ensemble. It's one of the stranger aspects of the Scarlet Speedster's comic book history, but also one of the most visually interesting.
The ring has been part of The Flash for as long as Barry Allen has been in existence, but it has gone through a number of ups and downs over the years in terms of the speedsters who have worn it.
The idea of a compressed costume fitting into a small space predates The Flash by a number of years. Batman, for example, hid his entire costume in a compressed container that was so small the vigilante was able to disguise in a bandage made to look like his skin. Granted, that was a special, lightweight version of the Caped Crusader's costume, but still, the idea was certainly there. However, the revelation that Superman used "super-compression" to squeeze his street clothes into his cape was introduced after The Flash's costume debuted. Not only that, but surely neither superhero displayed the same flair as The Flash does with his costume ring.
Amazingly enough, the ring practically predated The Flash's costume in his first story! In 1956's Showcase #4, by Robert Kanigher, Carmine Infantino and Joe Kubert, Barry Allen gains super-speed and decides he will become The Flash, based on the comic book hero of the same name from his childhood (yes, in the early stories, the Jay Garrick Flash was merely a comic book character), and seemingly the second thing he does is create a special chemical solution that will allow him to hide the costume in a special ring. It ostensibly operates on the same principles of inflatable life rafts, except it obviously doesn't work on any of those principles other than "it folds down small." As noted, in the context of Barry's origin story, the ring technically appeared before the costume, as we don't see the red-and-yellow suit until after it is released from the ring.
Like the classic question surrounding Peter Parker and his amazing web-shooters, you have to wonder how Barry is able to create a chemical in his spare time that can shrink a costume small enough to fit into a ring.
The creators clearly thought the ring idea was a good one, as they revisited it right away in the second story in the issue.
While it is not shown, it is implied that Barry uses his super-speed to re-fold the suit and places it back inside the ring when he returns to his civilian identity. Oddly enough, years later, it was revealed the suit is actually sucked back into the ring via the release of a special gas when the trinket is opened.
Barry continued to wear the costume ring until he died in 1985 in DC's Crisis on Infinite Earths #8.