This red dot sight is perfect for pistols and other compact Airsoft guns. When not in use it folds down into an extremely compact package; When you flip it up by pressing a lever on the side, it automatically turns on. It also has integrated iron sights in the event that the battery runs out. It comes with one CR2032 battery pre-installed.
Normally it attaches to Airsoft guns via two screws (via an RMR setup), which would require tapped holes in the frame of your Airsoft gun. An added bonus from ASRD with this sight is a picatinny rail adapter so you can attach it to any rail on any Airsoft gun.