Small groups connectivity & communication The SF4 is the perfect device for riding with friends by providing connectivity for small groups. The SF4 s 4-way intercom has a range over 1.2 kilometers (.80 miles) so you can easily stay connected with your group in open terrain. The SF4 also uses smartphone connectivity, allowing for music streaming, taking and making phone calls, and hearing turn-by-turn GPS directions. Most importantly, riders can listen to music and use the intercom simultaneously, using the Audio Overlay™ feature. Plus, with the Quick Charging capabilities, you will be ready to start your ride in no time. Smartphone Apps keep you connected Link the Sena SF4 Bluetooth device to the Sena SF Utility App (available for iPhone and Android) to easily configure device settings and quickly access guides. The SF4 Bluetooth device also connects to the Sena RideConnected App, which allows for communication with a virtually limitless amount of riders over an infinite range, so long as you are connected to a mobile network. General Talk time: 13 hours Operating temperature: -10?C ~ 55?C (14°F ~ 131°F) Dimensions: Speaker Driver Unit: 32 mm – thickness 10 mm Main Module: 73.3 mm x 38.7 mm x 16.6 mm (2.9 in x 1.5 in x 0.7 in) Wired Boom Microphone: length 183 mm Wire between Speakers: length 590 mm Weight: main 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) Audio Noise Cancellation: Advanced Noise Control™ Codec: Built-in SBC Codec FM Radio: Radio frequency specifications: 76 ~ 108MHz Intercom Working Distance: Up to 1.2 km (0.8 mi) in open terrain Supports up to 4 riders Battery Charging time: 1.5 hours Quick Charge: 30 minutes of charging equals 4 hours intercom Type: Lithium Polymer Battery