Feature: Super mini size, easy to carry and conceal. Very easy to use: simply call the SIM number installed in the device. Within seconds, you can hear audio from a 10-meter radius. GSM Quad Band (850/900/1800/1900 MHz) ensures worldwide compatibility. Built-in dual microphone design delivers clear sound quality for reliable performance. Supports preset phone numbers, including both landline and mobile numbers. Element type: Two-way audio device. Acoustic alarm function included. Long standby time: equipped with a built-in 200mAh lithium-ion battery, lasting 3-5 days with acoustic alarm enabled, and up to 12-15 days when disabled. Materials: Molded plastic. Dimensions: 4.3 x 3.2 x 1.4 cm. Power: Built-in 200mAh lithium-ion battery. Color: Black. Voice activation duration: 3-5 days with alarm on, 12-15 days with alarm off. Main function: Tri-Band GSM two-way audio monitoring device. Operating time: up to 5 hours. Microphone range: 5-7 meters radius. Package includes: 1x bidirectional audio device, 1x USB cable, 1x user guide (English and Chinese). Note: Color may vary slightly due to different screen settings.