Defender FreeMotion B571, headphones with microphone. Compactness and design at the same time, that's Defender FreeMotion. Defender brings us unbeatable headphones with beautiful LED backlighting in terms of price/performance. These headphones will delight all those who like to party with their friends or use headphones on multiple devices. Just fold them and you're good to go. A built-in microphone is used for communication, which can be controlled using buttons that are not on the side of the headphones. With a single press, you can answer a call, change music or turn off the headphones. For maximum comfort, the headband of the headphones can be adjusted as desired and the foam padding guarantees long hours of playing without feeling tired. The biggest surprise is that you can insert a MicroSD card into the headphones. Thanks to this, you don't need a phone, computer or MP3 player to listen to music. You just need to record your favorite music on a MicroSD card. The audio cable is of course included in the package and the battery life of up to 9 hours only underlines the quality of these headphones. Specifications: Connection type: Bluetooth built-in Li-polymer battery Sensitivity (headphones): 115 dB Sensitivity (microphone): -42 dB Frequency range (headphones): 20 20000 Hz Frequency range (microphone): 100 16000 Hz Range: 0 10 m Working time in talk / music listening mode: 9 h Connectors: Micro-USB for battery charging Color: gray Battery capacity: 400 mA h Bluetooth specification: V5.0 + EDR, A2DP, AVRCP, HFP, HSP Wireless transmission frequency: 2.402 2.48 GHz Diaphragm diameter: 40 mm.