Years ago, you would purchase regular 8 mm film as 25 foot lengths of a special 16 mm film, double 8 mm lengths, they were run through the camera twice, kind of like a cassette tape, one side then the other, 25 feet at a time. After processing these reels were slit lengthwise and spliced together and returned in their original boxes as 50 foot reels. There are no 25 foot reels!