Nikon SB-900 AF Speedlight Flash for Nikon Digital SLR Cameras High-quality flash for standalone use or as part of a comprehensive lighting system Commander mode controls up to 3 Speedlight groups or unlimited individual Speedlights 4 wireless channel options; prominent master and remote control switch for wireless operation Auto power zoom coverage ranges from 17 to 200mm (FX format) to 12 to 200mm (DX format) 3 light distribution patterns; measures 3 x 5.7 x 4.7 inches (W x H x D) and weighs 14.6 ounces