The B1 500 AirTTL is based on the popular D1 Air series of monolights, with the same professional and convenience features. The two major differences are the battery power and TTL camera/flash integration. Slip the optional Air Remote TTL-C transmitter onto their cameras hot shoe and point-and-shoot without taking a reading and testing. The B1 500 AirTTL exchangeable Lithium-ion battery allows for up to 220 flashes on a 2-hour charge with the 2.8A charger that is included. The battery has fuel gauge-type LEDs which makes it easy to monitor the remaining power.