The Sony WM-2, introduced in 1981, is a compact stereo cassette player that represents a significant advancement in the evolution of portable audio devices. As the successor to the TPS-L2, it was acclaimed for being the smallest stereo cassette player at the time, almost identical in size to the cassette it played. Notable for its innovative design, the WM-2 featured a direct drive mechanism which allowed the control buttons to be conveniently placed on the front of the device, accommodating easier use while on the go. The unique arrangement of mounting the tape heads in the lid, with the cassette inserted differently compared to its predecessor, contributed to its miniaturization. This design eliminated the need for the heads to retract, saving valuable space without compromising functionality. The power-operated head engagement mechanism enhanced the compactness further, allowing for shorter button travel. The internal components were robustly designed to ensure stability and performance, with enhancements made to the counter-rotating flywheel to facilitate better operation. The machine featured a single miniature stereo volume control, retained dual headphone sockets, and a tone switch for tape selection. Aesthetically, the WM-2 had a symmetrical design with no distinct front or back, ensuring an elegant look. It incorporated a battery compartment hidden within the cassette area to maintain its sleek silhouette and included an attractive plastic holder with a belt clip for easy transport. The WM-2 was particularly successful, selling approximately 1.5 million units, and was initially available in metallic grey, later expanding into black and red varieties.