The patented Swan Sleeves by A.R.M.S., Inc. - for all mil. spec. flat-top upper receivers - provides a platform for a variety of scope mounts via the A.R.M.S. standard mil. spec. dovetail type rail system.
In addition, they incorporate a unique flip-up rear sight (shown here in "up" position) that aligns with the existing front sight; always stays in battery and can't be knocked down by accident.
This rear sight provides an A2 type windage adjustment with std. 250-300m range zero and a new 500m horizon line setting.
