43m Guide Number at ISO 100 180 degree swivel head Wireless compatible The Canon Speedlite 430 EX II is a flashgun with a guide number of 43 meters at ISO 100, making it extremely useful for all Canon EOS DSLR owners shooting in lower light conditions. The 180 degree rotating head allows for maximum flexibility for redirecting or reflecting light, and the 24-105mm zoom head insures the power outlaid by the flash is comparable to the attached lens. The Canon Speedlite 430 EX II is compatible with the Canon wireless system, meaning it can be triggered by another flash or a compatible EOS DSLR allowing for the flash to work off camera and light another angle of the subject. The Canon Speedlite 430 EX II is an excellent choice for working in lower light conditions, or balancing exposure in unpredictable levels of illumination, and is perfect for the advancing photographer.