These are brand new studio strobes/flash set. The master strobe (could be used as a slave strobe) has a guide number of 29gn at ISO 100. The slave strobe has a guide number of 29gn as fill light. Both strobes could be triggered by a flash or infrared. The master strobe could be triggered by a sync cord (included). It also comes with a test button. These strobes work on 110v power outlet. The A/C swivel adapter provides the power source from your wall outlet. It also connects the umbrella to the light stand. You could easily adjust the shooting angle on the swivel adapter. The umbrellas will soften the light to give your images a professional look and get rid of the ugly shadows completely. This set works great with film or digital cameras and is ideal for in studio or on location shooting.