Square softboxes such as this model are suitable for general purpose use providing a soft gentle lighting effect the polyester used in the pro series is heat resistant to 400degc 752deg and hence usable with any type of flash or continual lighting head the interfit pro soft box range is designed to fit onto the majority of studio flash units and each box requires a speedring from a choice of ten speed rings free speedring when placing your order please select which speedring you requ