Use the medium Stay-Put Sandbag II from Phottix to keep your lights and modifiers in place, even when working outdoors on location. It ships empty, and can be filled with up to 6 kg of sand or other heavy material. Its saddlebag design is double zippered for easier filling of each side. A hand strap makes it easier to carry, and a clip and loop on the side allow multiple sandbags to be clipped together.