JG PEQ Battery Box. Fits any RIS rail. Holds a battery that specifically fits a certain type of gun with front wiring: Fits Echo 1 Zombat, JG 416 (and variants), and some other guns that use its 10.8v battery (not included). Or just use it for looks! May fit some really small batteries, but will not work with 9.6v nunchuck or mini 8.4v.