The Sony WM-FX21 is a portable cassette player and radio that combines a traditional tape playback system with FM/AM radio functionality. It features a compact design, making it easy to carry around. The device is powered by batteries, providing mobility for users who want to enjoy their music on the go. The WM-FX21 has an FM stereo and AM tuner, enabling a variety of listening options. It's equipped with a built-in microphone, allowing for voice recording directly onto cassette tapes. It also includes features like auto-reverse, which enables continuous playback without the need to manually flip the tape. The device is known for its user-friendly controls and durable build quality, which is typical of Sony products in this category. The headphone jack allows for private listening, and the device may support various cassette types, enhancing its usability for a range of consumers who appreciate the classic sound of cassette tapes.