U-notch, rear sight sets use the highly accurate, 3-dot pattern with two green, fiber optic dots at the rear for sharp contrast and quick sight acquisition in all light conditions. No drilling or tapping required for most rifle models. Dovetailed front and rear sights may require minor fitting. Rear slide/blade combo fits all standard size, Williams, adjustable, rear guide, open sight bases. Converts traditional, rear iron sights into Fire Sights. Aluminum blade contains a single, U-shaped, green, fiber optic rod for 2-dot accuracy. Use with existing, factory, front sight or with fiber optic, Williams Rifle Sight Bead found elsewhere. Use with Slide/Ghost Ring. Mfg: Williams Gun Sight SPECS: Aluminum, black anodized. 3/16" (4.8mm), 1/4" (6.4mm), and 5/16" (7.9mm) high.