Rail mounted reflex sight with 33mm lens.  Metal construction for durability with integral rail mount allen key secured for a smooth no snag profile.  Comes with rubber lens cover, battery and cleaning cloth.  Sight features three levels of illumination in 3 colours, green/red/blue.  There are also four different reticle shapes available with the adjustment under the rear.  Personally I find the blue best for snow conditions, red woodlands and green for urban.  Uses standard readily available batteries, no special cells to try to source.