Ultimate Ears BOOM 4. Passive radiator dimensions (W x D): 46.1 x 65.2 mm, Driver diameter: 4 cm. Sound pressure level (max): 85 dB. Connectivity technology: Wireless, Bluetooth profiles: A2DP, Bluetooth range: 45 m. Product type: Wireless stereo speaker, Product colour: Blue, Product design: Cylinder. Recommended use: Universal