Bestok Bluetooth Handfree Heaphones Motorbike Motorcycle Helmet Earphone Headset System with Dual Stereo Speakers MIC Devices(PRO1) Easy to use and installedIt is very easy to install into a helmet. Remove the side padding from the inside of the helmet (if it can be removed) and place the devices at the height of your ears. Linking and PairingTo use this product, it s necessary to pair it to the Bluetooth device you wish to connect it to (mobile phone, GPS navigator).Pairing is a process that only to be completed once Call Function when there is an incoming call, the speaker will provide an acoustic signal.you can control this function such as Answing through a voice command,Ending a call,Rejecting an incoming call,Redialling etc. Adjusting the volumeVolume perception may depending on the position and separation of the speakers from your ears, as well as the type of helmet and motorcycle, external conditions and other factors Warranty and Servicesany question , please contact us in anytime , we will replied within 24 hours