Gehmann Lens Holder 50,23mm lens holder allows a prescription lens to be fitted eye-side of your rear sight manufactured exclusively for our own latest irises with a detachable front thread and not carrying our 1.5x magnified diopter. The detachable steel front thread of your iris is removed with the factory spanner501’s adaptor thread is then screwed into the front of your Gehmann iris501, now with your iris mounted, is screwed into your rear sight after loosening the rail carrier’s Allen screwMount your prescription lens in the lens holder which may be slid off the rail for easier assemblyReposition the lens holder on the rail as required and lock it in placeThe positioning of the assembly on your rear sight is easily set as the attachment boss has radial adjustment and is simply secured with the Allen screw located in the front bodyContact us at 70822-33324, if the product is in pre-order status.