Optional mass storage is available on an unusual magnetic tape system based on standard 35 mm film stock coated with iron oxide (manufactured by Kodak). At the time this was in use by the film industry to record sound tracks. Elliott's factory at Borehamwood was close to the Elstree film studios which explains the use of the 35mm sprocketed media. The 1000-foot reels held 4096 blocks of 64 words per block (4096 x 64 x 39 = 10,223,616 bits, or the equivalent of about 1.3 megabytes).