Round Zoom Head design delivers the smoothest, most pleasing light ever to grace a speedlight Advanced technology keeps the flash cool even when under fire. The flash does not overheat easily, with heat dissipation through an innovative nano-glass face. Enjoy balanced fill-in flash with the included detachable sub-flash in perfect manual control 76 watt-second TTL exposure reliability Manual mode from Full power (1/1) down to 1/256 (in 81 steps) for Main and Sub-Flash for control freaks Features an advanced Li-Ion Polymer battery for speedy recycling and longer life with direct recharge of cell packs with USB convenience Approximately 500 full power flashes per charge Full power recycle time of fewer than 1.3 seconds Optional connectivity to the external Flashpoint BP-960 Lithium Battery Pack Power for extended continuous high-speed Superspeed recycling and longevity Eliminates troublesome Overheating via flashtube and reflector technology