Sight magnifier

A United States Coast Guard Maritime Law Enforcement Specialist with an EOTech holographic sight and a magnifier on a CQBR variant M4 carbine. The pictured magnifier is flipped in, and is magnifying the view through the sight.

A sight magnifier is an optical telescope that can be paired with a non-magnifying optical sight on a weapon to create a telescopic sight. They work with the parallel collimated reticle image produced by red dot sights and holographic weapon sights. They may synonymously be referred to as a red dot magnifier, reflex sight magnifier, holographic sight magnifier, or flip to side magnifiers.