The Witt by Livall helmets are made in a good quality, timeless design and equipped with modern hi-tech features. • 9 ventilation holes• Lightweight: only 398g• Fits headsize 54-57 cm• IPX4 waterproof SENSOR ACTIVATED LED LIGHT The LED taillight is sensor activated and switches on automatically.The turn signals are controlled via the remote control on the handlebars.BUILT-IN PHONE ONLY BH51MSBWith the built-in hands-free phone with stableBlueTooth connection allows you to talk on the phone while cycling.SPEAKER WITH QUALITY STEREO ONLY BH51MSBThe open speaker gives you good quality stereo sound without blockingfor traffic noises so you can still hear what is happening around you.SOS SMS MESSAGEIn the event of an accident, your family will be notified immediatelyin the form of an SMS with GPS coordinates via the Livall app.WALKIE TALKIE FUNCTION ONLY BH51MSBThe walkie-talkie feature lets you communicate with one orseveral other cyclists using the helmet\'s microphone and speakers.