Sennheiser's HD4. 40s give you superb sound quality and the fantastic freedom of a wireless connection. With intuitive ease of control, an elegant but robust design and built-in mic to allow hands-free calls on the go, this is the ideal audio companion for music aficionados. Stunning Sennheiser Sound These closed-back over-ear headphones produce a detailed, rich and powerful sound. Proprietary Sennheiser drivers see that the mids and trebles are delivered with clarity and dynamism while bass frequencies are warm and mighty. Read more… Bluetooth & NFC Say goodbye to a wired connection and feel the freedom. Connecting by Bluetooth or one-touch NFC, it's simple and quick to connect your smart device. State of the art wireless technology and AptX audio codecs ensure the quality Hi-Fi sound of Sennheiser is reliably reproduced without the need of cable clutter. Calls on the Go With a high quality microphone built into the headset you can easily switch between listening and talking so you can take hands-free calls on the go and nothing slows you down. Built-to-last Battery Charging via USB, the battery is built to easily last all day. It'll keep you in glorious wireless music for up to 25 hours. Quality Design Constructed from high quality materials, ergonomically-designed ear pads ensure superb audio delivery, and a comfortable listen, even over extended sessions. Controls mounted on the ear-cups make adjustment and call-handling simple and intuitive. And when you're done, the HD4. 40s fold away into the included carry case for easy storage.