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 to turn hollow surfaces into functional speakers. 2. Different sounds with different surfaces: Utilizing bone conduction technology, this speaker delivers a customizable audio experience. Experiment by placing it on various surfaces such as glass, wood, plastic containers, photo frames, or headphones to experience different sound characteristics. 3. Portability: Lightweight and compact design makes it easy to carry and use anywhere. 4. Small but powerful: When placed on suitable surfaces, the speaker can produce strong sound output up to 115 decibels, with customizable sound quality. Thin materials like plastic containers or buckets are recommended for optimal performance. 5. Multifunctional use: Supports music playback, podcasts, phone calls, conference calls, and gaming audio. Built-in FM radio allows you to tune into radio stations and enjoy audio content. Specifications: Capacity: 400mAh Functions: Bone Conduction Speaker, FM Radio Wireless Version: 5.0, A2DP, HFP Supports Wireless Stereo Built-in FM Radio Bone Conduction Transducer: 3Watt Frequency Range: 120Hz16kHz Built-in High-Sensitivity Microphone Battery: 400mAh Polymer Battery Charging Port: USB-C (not compatible with 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 in color between the product image and the actual item. Measurement error is +/- 13 cm.