The Speedotron Force 10 1000Ws Monolight (120) packs a true 1000 watt-seconds of power, with a guide number of 540 at ISO 100 (at a distance of 10'), and it can perform at 4 to 5 flashes per second at low power levels. All of the features you need in a monolight are here: recycle to full power in 1.6 seconds, with audible and visible signals, 8-stop variability of power in 1/3-stop increments, built-in photo cell slave, low voltage sync circuit (safe for digital cameras), a cooling fan, auto dump feature, and a visual "fail to flash" indicator. And it only weighs 8 lbs (3.6 kg). Supplied for use with 120VAC.