The tape is arranged in an infinite loop which traverses a central hub and crosses a tape head, usually under a pressure pad to assure proper tape contact. The tape is pulled by tension, and spooling is aided by a lubricant, usually graphite, on the back of the tape. The tape ends in a Stereo-Pak are not connected by a made of a conductive material as in the later "automatic" switching 8-track cartridges, therefore 4-track cartridge players had to be switched manually between programs 1 and 2 by a lever on the machine. Due to the method by which the tape is moved, it is impossible to rewind and often risky to fast forward a 4-track tape.