An ammo canister was a small container of small arms ammunition. Because of its miniature size, a canister was generally limited to one to two clips of ammo and a few grenades. During the Clone Wars and the Galactic Civil War, engineers and pilots commonly carried such canisters to readily resupply their allies with ammunition.
It was often designed with a glowing red line around its cap that blinked on and off along with the words "AMMO SUPPLY" printed in Aurebesh along its side.