- 2 semi-circular flash tubes with individual control - 6:1 to 1:6 power ratio in 1/2 stop steps - Built-in transmitter to control compatible Speedlites - Illuminated LCD display - Powered by 4 AA batteries (alkaline, lithium, Ni-Cd or Ni-MH) - Compatible with EF 50mm f/2.5 Compact Macro, EF 100mm f/2.8 Macro USM, EF 100 f/ 2.8 Macro and MP-E 65mm f/2.8 1-5x