product information: Headphones come in a variety of listening options. Built-in TF card slot, you can use it. TF / Micro SD card with loaded MP3 music, listen to songs directly on the earphones. Designed with Bluetooth 5.0 chipset, it has lower power consumption and higher compatibility. Compatible with all phones, tablets, laptops, any bluetooth enabled device or device with a 3.5mm audio jack. Built-in microphone: support hands-free calling and voice report caller ID. With the latest enhancements, your voice will sound clearer in noisy environments. 40mm diaphragm speaker driver, deep sound quality stereo, enjoy wireless high-quality music. Specification: Model: B39 Bluetooth version: V5.0. Music time: about 6 - 10 hours. Standby time: up to 20 days. battery capacity : 400mA Color: black red, red black, white, black. blue packing list: 1 x bluetooth headset 1 charging cable.