The  PS-22  is a universal night sight (UNS)  from ATN.   It  works  as  a  front-side attachment for day scopes, to convert your regular day scope into a night vision system. It has many benefits, the most obvious being the ability to use your already sighted day scope as a night sight.  It requires the use of a longer Picatinny mount on your rifle that would hold both the day scope and the PS-22.  The included ARMS mount will allow quick release for use with the PS-22.  An optional ring adapter helps to attach the day scope directly to the PS-22 (though it's not necessary for the  PS-22 operation). UNS sights allow conversion from day to night systems in less than 30 seconds, without special tools and without affecting a zero. Clean optics and high quality image intensifiers guarantee a clarity of the image and good resolution. Another important feature of PS-22 is its affordability. Where the PS-22 delivers a good alternative option. This sight is available with Gen 2 and Gen 3 image intensifiers to satisfy any night enthusiast.