The Perfect Dot tritium sights for Glock include a patent-pending injection-molded sleeve designed to not only hold the tritium vials securely but also create a brighter and more durable ring (the trademark Perfect Dot) for maximum visibility both at night and during the day. The ring housings are CNC-machined steel and black nitride coated. Made in the USA using Swiss tritium. Various ring colors and combinations are available. Professional gunsmith installation is recommended.