Affordable adjustable red dot sight from GK Tactical available at RedWolf Airsoft for US$47.00. This can readily fit airsoft guns equipped with 20mm rail mounts... "GK Tactical Adjustable Red Dot Sight fits on a low profile mount, suitable for standard 20mm rail mounts. This small reflex sight is perfect for those of you looking to go minimalistic with accessories, featuring the sensor that means once you have inserted the battery, you are all set to aim and terminate your targets.

Package includes hex key for red dot adjustment and a rubber protective cover for the rod dot."