Phonograph cylinders are the earliest commercial medium for recording and reproducing sound. Commonly known simply as "records" in their era of greatest popularity (c. 1896–1915), these hollow cylindrical objects have an audio recording engraved on the outside surface, which can be reproduced when they are played on a mechanical cylinder phonograph. In the 1910s, the competing disc record system triumphed in the marketplace to become the dominant commercial audio medium.