Features: 1. Turn any hollow core into a speaker: These bone conduction speakers are compact and versatile, enabling a unique audio experience in various environments. Use them to transform everyday objects into functional speakers. 2. Different sounds with different surfaces: Utilizing bone conduction technology, this speaker delivers a customizable audio experience. Sound varies when attached to different materials such as glass, wood, plastic, or metal—like experimenting with different acoustic instruments. Test on items like glasses, guitars, paper boxes, plastic containers, photo frames, headphones, or dashboards for diverse audio effects. 3. Portability: Lightweight and compact design makes it easy to carry and use anywhere. 4. Small but powerful: When paired with suitable resonant surfaces, the speaker can produce strong sound output up to 115 decibels, with customizable sound quality. Thin, hollow objects such as plastic containers or buckets are recommended for optimal performance. 5. Multifunctional use: Ideal for listening to music, podcasts, making hands-free calls, joining conference calls, or enhancing gaming audio. Built-in FM radio allows direct radio playback. Specifications: Capacity: 400mAh Functions: Bone Conduction Speaker, FM Radio Wireless Version: 5.0, A2DP, HFP Stereo Audio Support: Yes Built-in FM Radio: Yes Bone Conduction Transducer: 3Watt Frequency Range: 120Hz - 16kHz Built-in High-Sensitivity Microphone: Yes Battery: 400mAh Polymer Battery Charging Port: USB-C (does not support fast charging) Note: For best FM radio performance, use outdoors and connect the USB cable during use. Material: Metal Color: Black Package Contents: 1 x Bone Conduction Speaker 1 x Charging Cable Note: Light reflection and display differences may cause slight color variations between the image and the actual item. Measurement tolerance: +/- 1-3cm.