The Bower SFDRF Ringlight Flash is a round ringlight flash with a guide number of 59' at ISO 100 that mounts onto the front of a lens. It is ideal for macro photography. It is designed to work with digital SLR cameras as well as with film cameras. The standard ring size is 52mm. The unit comes with 55, 58, and 62mm adapter rings and runs on 4 AA batteries.