This is a AmeriGlo Sight Tool known as the Protector, model GL-705.
Employing a glare-reducing black serrated rear sight paired with a tritium ProGlo front sight" the Protector Sights are designed for quicker front sight acquisition and maximized concentration on the front sight blade.
Features:
Green tritium .140 wide with LumiGreen outline front
Black serrated .150 wide square notch rear