The Holosun HS510C red dot represents the segment of open reflex sights. This means that it has only one (front) lens on which the sight mark is cast. This ensures a very wide field of view and no keyhole effect, making its use more like aiming through a widescreen TV. Despite the open design, the HS510C has a very solid casing and an additional hood over the lens made of titanium, which can take any blows.