Rider to Passenger or Small Group Communication For riders looking to communicate with their passenger, the SF2 provides simple Rider to Passenger 2-way intercom communication up to 800 m (880 yards) in open terrain. For those who ride in small groups, the SF4 is equipped with 4-way intercom over 1.2 kilometers (0.8 miles). Both models let riders enjoy smartphone connectivity. Riders can listen to music and use the intercom simultaneously using the Audio Overlay™ feature. Please note that Audio Overlay works best with Android devices, while iOS offers limited functionality. General Talk time: 13 hours Operating temperature: -10?C ~ 55?C (14°F ~ 131°F) Dimensions: Speaker: driver unit 38 mm – thickness 10 mm Wired Boom microphone: length 183 mm Wire between speakers: length 590 mm Weight: Module: 35 g (1.23 oz) Bluetooth Bluetooth 4.1 Headset Profile (HSP) Hands-Free Profile (HFP) Advanced Audio Distribution Profile (A2DP) Audio Video Remote Control Profile (AVRCP) Intercom Working distance: SF4 - up to 1.2 km (0.8 miles) in open terrain SF2 - up to 800 m (880 yards) in open terrain Audio Advanced Noise Control™ Built-in SBC Codec Wide volume control Sample rate: max. 48 kHz (DAC) FM-Radio Built-in FM radio with RDS AF (Radio Data System Alternate Frequencies) Radio region: worldwide Radio frequency specifications: 64 ~ 108MHz 10 preset station memory with automatic scan function Battery Charging time: 1.5 hours Quick Charge: 30 minutes of charging equals 4 hours intercom Type: Lithium polymer Certificates FCC, IC