The Bowens Travelpak Control Panel is what makes the "hot swap" Travelpak work--Travelpak portable batteries (not included) will power the Gemini monolight (not included) miles from any electrical outlet, but what makes them unique is the ability to swap a fresh Travelpak battery for a depleted one in the time it takes to switch the control panel from the top of one to the other without waiting for a battery to re-charge. You save time and you don"t lose crucial momentum in the middle of a shoot. This control panel fits both the small and the large Travelpak. It quickly and easily clips and unclips to the top of the battery.