The 29mm Optum packs all the features a shooter could need into a small, efficient, and lightweight package The ORS or Optum Ring System is a removable ring system that offers eight pin positions and lets the shooter swap between pin sizes and fiber colors in seconds Adjustable rheostat fiber covers offer complete control over ambient lighting 8-32 threaded holes allow an electronic light kit to illuminate the fiber and pin An angled 8-32 threaded light port enables the user to shine a light on the center of the lens Lens housing for the 29mm Optum scope (sold separately) Accepts lenses from 1.25” to 1.35” in diameter (does not include a lens) Fiber bypass slots in the ring system permit fiber to wrap around the scope completely in order to collect more natural light Interchangeable levels let users swap between different colors to best suit their needs Threads on either end of the scope accept a variety of sunshades and lenses for even further customization Made in the USA