ISO 24537:2007 covers the essential dimensions of lightweight reels, made of plastic or metal, used for the storage and retrieval of processed 16 mm and 35 mm microfilm that is used in manually threaded equipment.
Reels intended for use in 16 mm automated retrieval systems are outside the scope of ISO 24537:2007. The dimensions of these reels are specified in ISO 7761.
Camera spools are also frequently used for storing processed microfilm. The dimensions of these spools are outside the scope of ISO 24537:2007, but they are specified in ISO 6148.