Features: 1. Turn any hollow core into a speaker: These bone conduction speakers are compact and versatile, allowing you to enjoy a unique sound experience in various environments. Use them with different hollow objects to create audio output. 2. Different sounds with different surfaces: Utilizing bone conduction technology, this speaker delivers a customizable audio experience. Experiment by attaching it to various surfaces such as glass, wood, plastic containers, photo frames, or headphones to achieve distinct sound effects. 3. Portability: The device is small and lightweight, making it easy to carry and use on the go. 4. Small but powerful: When paired with suitable materials like thin plastic or hollow objects, the speaker can produce strong sound output up to 115 decibels, with adjustable sound quality. 5. Multifunctional use: Supports music playback, podcasts, hands-free calling, conference calls, and gaming audio. Includes built-in FM radio functionality for listening to radio stations. Specifications: Capacity: 400mAh Functions: Bone Conduction Speaker, FM Radio Wireless Version: 5.0, A2DP, HFP Supports Wireless Stereo Audio Built-in FM Radio Bone Conduction Transducer: 3W Frequency Range: 120Hz - 16kHz Built-in High-Sensitivity Microphone Battery: 400mAh Polymer Battery Charging Port: USB-C (does not support fast charging) Recommended to use FM function outdoors; connect USB cable for stable performance Material: Metal Color: Black Package Contents: 1 x Bone Conduction Speaker 1 x Charging Cable Note: Light reflection and differences in display screens may cause slight variations between the color shown in the image and the actual product. Measurement may vary by +/- 1-3cm.