Yongnuo YN-E3-RT Flash Speedlite Transmitter for Canon 600EX-RT as ST-E3-RT Power Source: 2 AA/LR6 alkaline batteries Ni-MH batteries Wireless flash shooting time: Approx. time: 10 continuous hours ** when using AA/LR6 alkaline batteries Power saving: Power off after 5 min. of idel operation Weight: Approx.110g(transmitter only, excluding batteries)