The tape was coated with a slippery backing material patented by Cousino, usually graphite, to ease the continuous slip between the tape layers. This coating sometimes also caused the pinch roller to slip, leading to poor speed control and tape flutter. Due to these problems, 4-track cartridges were never popular with audiophiles. While the design allowed simple and cheap players, unlike a two-reel system it didn't permit winding of the tape in either direction. Some players offered a limited fast-forward by speeding up the motor while cutting off the audio but rewinding was impossible.