[Source] The SW-4 was a dual ion cannon manufactured by ArMek during the early years of the Galactic Empire. It was most commonly used aboard BTL Y-wing starfighters of the Alliance to Restore the Republic. The SW-4 ion cannon was a notoriously delicate weapon system, and its internal crystal matrices invariably vibrated out of alignment during flight or combat. Rebel mechanics came to dislike the SW-4 due to the time they were forced to put in to maintain the cannons. At the Battle of Yavin, only two of the Alliance's Y-wing fighters had functional ion cannons.