APS Folding Battle Rear Sight Fits For All M4 M16 AR-Series Rifles Airsoft with standard 20mm RIS/RAS railAPS Folding Battle Rear Sight Fits For All M4 M16 AR Series Rifles Airsoft with standard 20mm RIS RAS rail Made out of Alloy metal. Troy type folding battle rear sight. Suitable for all M4 M16 & AR Series with standard 20mm RIS RAS rail. Install on the 20mm rail with a large thumb screw. Windage adjustment by thumb dial. Large and small holes flip selection for 300 & 600 meters aiming. Spring Loaded Flip Up system. Solid click sound when sights are