Sennheiser HDR 185 Accessory RF Wireless Headphone for RS 185 System Audiophile style open back, circumaural headphone system.Connectivity Technology: Wireless High-performance Sennheiser transducers deliver precise, detailed and dynamic sound Designed exclusively for use with the RS 185 RF Wireless Headphone system (sold separately) Two year warranty when purchased from an authorized Sennheiser dealer. Connectivity technology: Radio Frequency wireless