Wikipedia
SUSAT
The Sight Unit Small Arms, Trilux, or SUSAT, is a 4× telescopic sight with tritium-powered illumination, utilised at dusk or dawn. The full name of the current model is the SUSAT L9A1. The sight is not designed as a sniper sight, but is rather intended to be mounted on a variety of rifles and to be used by all infantrymen. A similar device is the Advanced Combat Optical Gunsight.