G&G Rotary Hop Up M4 Chamber Lasers Uses a CR1620 battery (included)

Uses a CR1620 battery (included) for the dot illumination

The Airtech Studios G&G ARP9 / ARP556 BEU Battery Extension Unit is designed to fit on G&G ARP series of AEG guns:  fits on the ARP9 and ARP556

Optional batteries would be a 9

or you can extend the stock and use both hands for added accuracy

Works with Airsoft versions as well

G&G Rotary Hop Up M4 Chamber Lasers Uses a CR1620 battery (included)The G&G Rotary Hop Up M4 Chamber is a rotary style for M4 and M16 style airsoft guns. New for 2017, this is a great hop up chamber for those that want to upgrade from their factory's original. Includes chamber and c clip. Bucking and rubber units not included. Made by G&G in Taiwan.