For a durable and compact flip-up rear A2 iron sight the NcSTAR MARFLR is the AR-15 back-up rear iron sight that you're looking for.
- Precision made flip-up A2 rear sight. The MARFLR will fit virtually all AR-15, M4, and M16 flattop Picatinny rail upper receivers. - A2 rear sight assembly with large and small rear aperture. A2 rear sight is fully adjustable for windage with knurled click adjustable controls. - Large steel thumb nut and precise rail clamp for positive & secure attachment to your upper receiver. - With the MARFLR flip-up sight folded down, it's 1 7/8 Length X 11/16 Height (mount height) & 1 1/16 Height (A2 sight base when folded)