First appearance: Showcase #4 (October, 1956)
History: Flash's Costume Ring is a small ring with a spring-loaded opening. Barry Allen, the second Flash, used this ring to compress and conceal his costume while operating in his civilian identity. By thumbing a small stud on the side, the top of the ring opened, releasing the costume (chemically treated to shrink), allowing Barry the ability to change clothes at super-speed.
How it Works: The Flash's alter ego, Barry Allen,
is a research chemist who is accustomed to fabricating his own test
equipment. The suit-concealment ring and repeatably-compressible suit
was a great challenge. The ring is a combination of miniature machining
and traditional lost-wax jewelry casting and is made of a high grade
stainless steel. For the Flash's costume, Allen developed a thermally
stable costume, suitable for high speed travel. The suit is made of
highly compressible synthetic silk with ultrasonic welded components.
The key to the suit's effectiveness is bonded outer layer of
ultra-smooth Teflon which aids in thermal dissipation and eases the high
speed passage through atmosphere or other media. The suit fits into the
ring through a series of carefully calculated foldings. The suit is
compressed so rapidly that great heat is developed as it is placed
inside the ring. As the suit cools, a partial vacuum is formed which
holds the ring halves closed. The suit forms its own seal against the
only opening, which is the release stud. When the ring is opened, the
synthetic silk molecules uncoil and absorb atmospheric gases, expanding
to full size very rapidly
Wally West, the third Flash, also uses one of these rings. Barry's grandson, Bart Allen, used a similar ring to hide his costume while he was the Flash, and another to house his Impulse and Kid Flash costumes (he does not remove this ring under any circumstances, at least not willingly). Bart's first costume ring, that in which he stored his Impulse costume, was a gift from Wally West, and a replica of Barry's original.
Other Non-Flash Rings: Barry
Allen gave Flash Costume Rings to other members of the Justice League,
containing their own costumes, as seen when Green Arrow has Arsenal steal the one Green Arrow had gotten from Barry, which had been in the Flash Muesum's collection "Friends of the Flash". His costume is stored inside of it and it says "To Ollie, Run fast. - Barry". Ollie makes it into his engagement ring for Dinah. The other members of the Justice League didn't use them because they weren't fast enough to get into their costumes.
Fun Fact: Green Arrow used the ring given to him by Barry Allen as a gift when he proposed to his longtime girlfriend Black Canary.
Fun Fact: The Flash has shown the ability to vibrate and compress his molecules to actually hide himself inside of the ring when the situation calls for it.