"With the K550s, AKG engineers have struck a masterful balance between the noise-isolating qualities of closed-back headphones and the spacious, dimensional sound of an open-back design creating reference-class headphones ideal for private listening both at home and on the go. 50mm drivers, the largest in our product line, deliver great AKG sound from your hi-fi system or virtually any portable device.The large ear cups and new headband design ensure an amazingly comfortable fit, and the 2D-axis mechanism folds flat to stow or go."