[Source] The PX-4 was a type of proton torpedo first produced by Merr-Sonn Munitions, Inc. during the Galactic War between the Republic and the Sith Empire. The PX-4 was capable of locking onto targets at an extreme range and dealing massive damage to enemy starships, as it ripped through both shields and armor. The torpedo's drawbacks included a narrow lock-on targeting cone, a lengthy lock-on period, and a limited ammunition capacity for its launcher.