This is a Trijicon Sight known as the Bright & Tough, model SA39-C-600714.
S&W M&P Shield(TM) Night Sight Set (Green Front & Rear Lamps): Trijicon Bright & Tough Night Sights are three-dot iron sights that increase night-fire shooting accuracy by as much as five times over conventional sights. Equally impressive" they do so with the same speed as instinctive shooting - and without the need for batteries. Housed in a metal body and cushioned within silicone rubber" Bright & Tough Night Sights feature a unique shock-resistant design. Each lamp is capped with a sapphire jewel to help evenly distribute the light while protecting the lamp from solvents and puncture. Contained within aluminum cylinders for additional protection" the lamps are mounted on silicone rubber cushions to withstand shock and heavy recoil. Green lamps are warranted for 12 years from the date of manufacture.
Features:
Professional installation recommended
Fits Smith & Wesson Shield .40 .45 and 9mm models;Tritium-Phosphor lamp;Sapphire window;Silicone rubber cushion;Protective aluminum cylinders;White rings;Suppressor sights