Meprolight has solved the aiming limitation by developing the first and only optical for 40mm Grenade Launchers. The MEPRO GLS sight functions under all lighting and weather conditions, and offers soldiers the ability to accurately aim and hit targets with both eyes open. The self-illuminated optical sight is a real technological breakthrough. The compact unit mounts onto the Picatinny top rail - on its own or behind the MEPRO M21 Reflex Sight and can also be mounted onto a side adapter (9 o'clock). It is adjustable for both windage and elevation. During the day, a light collector tube concentrates available ambient light into a dot and projects it onto the sight lens. At night, a small tritium light source supplies the light for the dot.