The ST Kinetics SAR 21 (Singapore Assault Rifle - 21st Century) is a Singaporean bullpup Assault Rifle developed in the early 90s and later adopted by the Singapore Armed Forces in 1999. Designed to counter weaknesses of the SAF's former M16S1 rifle, the rifle uses a modified Stoner operating system with higher reliability and produces lower recoil than the M16. It is constructed out of high-impact polymer and features a built in 1.5x optical sight.
The SAR 21 MMS (Modular Mounting System) variant has a shorter barrel length and replaces the SAR 21's built in sight with a Picatinny rail system to allow mounting of various other optics and accessories.
The SAR 21 appears in two games in the Battlefield series. The model of the SAR-21 used in the games combines the rail system of the MMS variant with the barrel length of the standard variant.