Night Fision's patented injection molded sleeve design holds their tritium vials securely in place using ballistic materials. Night Fision night sights carry more tritium than the average night sight on the market and a domed lens engineered to create the a crisp, defined glow. Domed lens collimates tritium rays for a sharper sight picture Built in the USA with Swiss Tritium Black Nitride coating used to improve wear and corrosion resistance Perfect Dot Night Sights with added daytime florescent or phosphorescent ring