... distance: 20~25m indoor, 10~15m outdoorSlave groups: 3(A, B, and C)Channels: 4Zoom range: auto, 24, 28, 35, 50, ... levels of fine tuningExternal interface: hot shoe, PC port and eternal charging portExternal power: YONGNUO external charging boxes like SF ... setting, automatically saving setting, PC port, power saving mode and over heat protectionDimensions: 60×190×78mm (Extended state)Net weight ...