This somewhat higher power flash has a few other additions, as well. Guide Number is 64 ft (20m, ISO 100). To put that in perspective, since Aperture = GN / Distance, at f/4 that would give you the ability to fully light a subject at about 16 feet (3m). The flash head can be tilted up to bounce and has a built-in diffuser with wide angle and telephoto positions. This flash mounts to and draws power from the camera's accessory port. Includes soft carrying case. US$150.