About this item ~ Size: Medium ~ Matte Gray ~ **Disclaimer: The box is not in the best of shape, just want to be transparent** 4-Way Bluetooth Intercom for hands-free helmet-to-helmet communication.Speakers & Microphone built-in, no installation needed.Integrated Taillight with 3 brightness settings for rider visibility.Smartphone Connectivity in order to listen to music, turn-by-turn directions, take calls, and more.Compatible with the Sena Cycling App for adjusting settings, smart intercom pairing, and access to quick start guide. Age grade: Adult US FOR C1 Brand SizeHead Circumference (in) M 21.3 - 22.9 L 22.9 - 23.8