The power pack offers 7 F-stops of manual control and has a bright, seven light battery gauge and a TTL setting with optional audible confirmation. The very low power settings help with faster film speeds, digital cameras and confined spaces, plus they conserve battery power. TTL is accomplished by using optional Metz brand SCA TTL adapters plugged into the flash head. One or two flash heads may be used in manual or TTL without needing extra adapters. The head included in this kit has a 25 watt modeling light, and can handle up to 800 w/s of stored power.