UK Pom Poms are the fast firing, low damage anti-aircraft gun used by most RN players as AA. They have a very steep golden angle at around 51~52 degrees, making them perfect to counter the diving bombers.
Don't rely on them, they're notorious for jamming. The game. When ~5 players start hammering the skies.
Also, they're useless against ships unlike the 20mm of the German U-Flak, which has the same sprite.
They are only usable by the UK AA gunners classed above level 45. And makes a terrific noise that sounds very similar to a fully automatic rifle.