The Leupold Mark AR MOD 1 delivers extreme clarity from edge to edge of the visual field, outstanding contrast, and a bright sight picture even in extreme low-light conditions. Features include an exclusive, proprietary Argon/Krypton gas blend, which nearly eliminates the effects of thermal shock, and reduces the diffusion of gases sealed inside your scope even more than our proven nitrogen technology already does. The Leupold Mark MR MOD delivers.