This is a XS Sights Sight known as the Big Dot Tritium Front, model SI-0013S-5N.
XS DXT2 Big Dot Night Sights offer the best front sight visibility in all lighting conditions. DXT2 Big Dot sights drive focus to the front sight using a high-contrast front and a V-notch rear for an unobstructed view of the front sight. DXT2 Big Dot front sights use a patent pending glow dot that absorbs light and glows in low light levels before it is dark enough to see the tritium. Optic Orange is designed to offer a high-contrast sight picture when shooting in bright light conditions and maintain its visibility in decreasing light levels. To ensure visibility in low light when uncharged" optic orange is primarily based on yellow with a hint of red. The increased surface area of the convex dot increases light absorption" intensifying the charge of the glow properties of the dot. The dot-the "i" sight picture" with a tritium dot in the front sight and a tritium bar in the rear" prevents confusing the front and rear sight in high-stress situations. The wide field of view increases visibility of the front sight and of the threat downrange.
Features:
Tritium powered front and rear sight
Orange outline front
V-notch rear
Rear sight white outline