Easy-to-install front sights for popular centerfire and muzzleloading rifles gather ambient light for superb visibility. The more light, the brighter the round, red beads glow; won't "wash out" even in the strongest sunlight. Medium sights fit most factory ramps including Marlin and Remington. Mfg: Williams Gun Sight SPECS: Blued steel. Fiber optic insert. Beads: 1/16" (1.6mm) dia. Fit nominal 3/8" dovetail. Number indicates height – Height measured from bottom of dovetail to top of sight; letter (N, M or W) indicates base width: M Series – .340" (8.6mm) wide base.