This beta cloth bag was used to store the auxiliary lights associated with the production of IMAX and presumably other films aboard the Space Shuttle. In the microgravity environment, stowage bags like this are used to restrain just about all equipment and provide a buffer between metal lockers and cabinets and the equipment they contain.
NASA transferred this and other IMAX film equipment to the Smithsonian in 2012.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.