The popular SIG P365 has a proprietary rail that prevents standard rail-mounted accessories from fitting it. This C5L Custom was designed specifically for the SIG P365 by the expert engineers at Viridian. Viridian has collaborative relationships with the major gun manufacturers allowing for the ultimate custom fits on the custom C Series and also the extensive line of red and green E Series. Nobody has more custom-fit accessories than Viridian and nobody does it better.