The Muse Coolbox is a stand alone unit which includes a water pump, water reservoir, and air compressor components. It is an updated, more convenient alternative to the hobby kit, which is a water pump that needs to be placed in a bucket and a separate air compressor. The Coolbox encapsulates everything you need to safely run the laser. The right choice for the serious laser user. NOTE: We recommend the Coolbox but if you have an existing water pump, reservoir and air compressor this is not a required accessory.