Arms Low Profile Flip Up Rear Sight

The A.R.M.S., Inc. #40L Low Profile Flip Up Rear Sight is a compact, low-profile backup aperture sight engineered for flat-top AR receivers where optical mount real estate is critical. Unlike standard height rear sights that obstruct optic placement, the #40L achieves a collapsed height of just 0.610 inches, preserving your ability to mount low-power variables, red dots, or precision scopes while maintaining a fully functional iron sight backup system.

The sight features a dual aperture design paired with a miniaturized windage knob calibrated in 0.75 MOA increments, enabling precise point-of-aim adjustments without removing your optic from the gun. The rear-leaning design ensures the sight folds in the correct direction if impacted, maintaining zero retention across range sessions and field operations. This geometry is deliberate—when a folded sight takes impact, it closes fully rather than binding or developing play that compromises accuracy on follow-up shots.

Purpose-built for operators and competitive shooters who rely on co-witnessed backup irons, patrol rifles configured for primary optics, and precision platforms where mounting flexibility matters. The low-profile rear sight class addresses a specific requirement: maintaining iron sight backup capability without sacrificing optic height or requiring canted mounts. Users report the compact profile leaves adequate rail space for additional accessories while the dual aperture setup accommodates both close-quarters engagement and intermediate-distance shooting from supported positions.

A.R.M.S. flip-up rear sights occupy a recognized position in the backup iron sight market, preferred by users who prioritize fold-flat design and positive detent action. The #40L variant compresses the sight further than standard 40A2 configurations, making it the explicit choice when optic real estate is finite or when maintaining a lower sight plane improves ergonomics with your primary optic's eye relief and field of view.