1. 360° Rotatable USB Computer Volume Controller This usb volume knob features a 360° Rotatable knob for precise volume adjustments and a onetouch mute function, providing you with convenient control over your computer's audio output. 2. BT USB Volume Knob for PC Equipped with BT 5.1 Chip, this volume control for pc allows you to effortlessly pair your computer with BTenabled headphones or speakers, ensuring a seamless and quick connection for wireless listening. 3. USB Decoding Player This U disk player supports a wide range of audio formats including MP3, WAV, WMA, APE, and FLAC. It also features like fast forward, rewind, and folder switching for enjoying your music in various ways. 4. External Sound Card Adapter In external sound card mode, you can plug your headphones into the 3.5mm headphone jack to listen to your computer's sound without having to crawl under the desk to find the headphone jack.