There are several other differences between CD-ROMs and disk drives. The most obvious is that CD-ROMs, once written, cannot be rewritten because there is no way to fill in the microscopic holes again. Another difference is that the holes are arranged in a spiral, rather than concentric circles. Old vinyl phonograph records, using diamond needle tone arms as the read head, also used a spiral so that the needle would not have to be lifted out of the current track and put into the next one. However, CD-ROM readers start from the center and move outwards, whereas phonographs start at the edge and spiral inwards.