Sennheiser PX 100 Lightweight Collapsible Headphones (Discontinued by Manufacturer) Super lightweight design Rugged collapsible headphone with case Warm natural sound for all types of music Collapsible open-air headphones High energy driver system for max performance Collapsible open-air headphones Warm natural sound for all types of music High energy driver system for max performance Rugged collapsible headphone with case Super lightweight design