Sennheiser RR 4200. Ear coupling: intraaural, Wearing style: In-ear, Headphone frequency: 50 - 16000 Hz. Connectivity technology: Wireless, Headphone connectivity: 3.5 mm, Wireless technology: RF. Dimensions (WxDxH): 200 x 135 x 20 mm, Weight: 53 g. Battery life (max): 9 h, Battery recharge time: 3 h, Battery technology: Lithium Polymer (LiPo). Playtime internal battery: 9 h