Sennheiser One Ear Smartphone Headset
HD231i

Closed headset design with dynamic bass for noise isolation.
Smart in-line remote control with microphone - change the volume， control your music-playing options， answer or end calls and activate Voice Control - all from a sleek built-in unit
Powerful Sennheiser bass - the dynamic speaker system with neodymium magnets delivers bombastic bass-driven stereo sound
Customized fit - the ear cups are individually adjustable so you have a comfortable， secure fit
Ultra comfortable - the large cushioned ear pads and headband keep you going， however long the commute
Made for latest generations of iPod， iPhone and the iPad*
Peace of mind - thanks to the 2-year international warranty

What's in the box?
HD 231i headset/Quick start guide

Specifications
Impedance 32 Ω 
Connector 3.5 mm plug， straight 
Frequency response (Headphones) 19 – 21000 Hz 
Sound pressure level (SPL) 108 dB 
THD， total harmonic distortion < 0，5 % 
Ear coupling Supra-aural 
Cable length 1，2 m 
Weight ~ 92 g 
Sensitivity as per 121 TR 9-5 -40 dBV/Pa 
Transducer principle (headphones) dynamic