Why choose Motorcycle flip-up Bluetooth helmets? 1.High polymer ABS material, anti-collision and impact resistance. 2.High quality inner lining, sweat-absorbent, detachable, detachable and not stuffy when wearing for a long time. 3.PC sun visor, high definition anti-ultraviolet rays. Adapt to various bad weather riding. 4.Bluetooth: charging time is about 4 hours, standby time is 80 hours, lasting work is about 10 hours. 5.The principle of aerodynamics, has good ventilation and can keep your head comfortable at all times. 6.Certification: ECE 22.05 / DOTFMVSS-218 certification Bluetooth-Parameter: 1.Bluetooth-Version: V5.1 + EDR 2. Frequenzbereich: 2,4026 GHz-2,480 GHz 3. Übertragungsentfernung: mehr als 10M 4. MIC-Abstand: ≤1m 5.Schlüsselbatterie: 3.7V/1200mA 6. Ladezeit: 5 Stunden 7. Standby-Zeit: ca. 128 Stunden 8. Kontinuierliche Arbeitszeit: ca. 20 Stunden Name: flip-up helmets Size: M=57~58cm, L=59~60cm, XL=61~62cm，XL=63~64cm Weight: 1500±50g Package includes: 1 * Motorcycle Bluetooth Helmet ◆ Notes: ★ The product size is measured manually, there may be a slight error. I hope you can understand, thanks! ◆ Customer Service: ★ If you have any questions, please email us, we will reply you within 24 hours and provide you with the best solution.