Short for ‘sprocketed magnetic film’. Can have either an acetate or polyester base, and from one to six tracks, depending upon the head stack used. Three-track head gaps are 200 mils wide, the equal of half-inch 2-track tape; 35mm 4-track is 150 mils wide, and 6-track is 100 mils wide, where 8-track 1-inch or 16-track 2-inch are 70 mils. (For point of reference, 24-track 2-inch head gaps are 43 mils wide.)
The oxide coating is very thick, varying from three to five mils. There is also ‘stripe’, which has two magnetic stripes on a base of clear film. One stripe is large and contains a single track of audio (in the same size and location as track one of a 3-track), while the other stripe is smaller and exists only to make the film pack evenly when wound together, hence the term ‘balance stripe’. The balance stripe is sometimes used to record timecode from 1/4-inch or DAT timecoded production masters. Fullcoat is mag film that is covered edge-to-edge by the magnetic oxide.