The Thermal Weapon Sight (TWS) is a lightweight, low power, high performance forward looking infrared (FLIR) device that will augment existing crew-served night vision sights. TWS is completely passive and although primarily designed for target detection and engagement with individual and crew-served weapons, it can also be utilized for all weather surveillance. The U.S. Marine Corps is procuring both the Medium Weapon Thermal Sight (AN/PAS-13B (V) 2) and the Heavy Weapon Thermal Sight (AN/PAS-13B (V)3). The MWTS can effectively engage targets out to 1000 meters while the HWTS can effectively engage targets out to 2000 meters.
The MWTS will be mounted to the M249 Squad Automatic Weapon (SAW) and M240G Medium Machine Gun. The HWTS is intended to be mounted to the M2 .50 cal Heavy Machine Gun, and MK19 40mm Machine Gun.
These items are being replaced by the AN/PAS-13D (V) 2 Medium Weapon Thermal Sight (MWTS) and (V) 3 Heavy Weapon Thermal Sight (HWTS)