VPR Illuminated Reticle with Zero Stop - 34mm Tube Arken Products are designed to combine quality, performance and precision with tremendous value. The SH4 is a FFP (First Focal Plane) optic that features a simple but rugged zero stop mechanism. The Arken SH4 incorporates adjustable elevation and windage turrets with tactile and audible clicks. These turrets offer 8 mils/20 moa per revolution.