Sigma Electronic Flash EF 500 DG Super SA-N Flash attachment for Sigma, Canon, Minolta, and Nikon AF 35mm SLR and Digital SLR cameras Guide number 165 Built-in diffuser expands illumination angle down to that of 17mm lens Can be tilted 90 upwards for bounce flash and 7 downward for close-ups Powered by 4 AA-size batteries