iKross Portable Bluetooth Wireless Handsfree Microphone Headset for ZTE ZMax Answer / End / Reject call, Comes with On/Off button. Volumn control Bluetooth version: 3.0, Supported profiles: HSP, HFP, A2DP. Talk time: up to 4 hours. Standby time: up to 125 hours. SIZE: 1.22 x 0.63 x 0.43 inches (31 x 16 x 11mm). Compatible with Most Bluetooth Enable Cell Phone, Smartphone Tablet