Upgraded 4 People Group Intercom: This referee communication system allows 4 referees to connect at the same time in a maximum intercom range of 1500 meters. 4 referees can talk at the same time and keep in touch with the situation on the field freely. | Clear and Stable Sound: With improved CVC noise cancellation technology, it reduces surrounding wind and background noise including whistles. So that the sound you hear is more clear and stable even in a noisy stadium. | Wide Applications: V4Plus is an excellent partner for most competition referees like football referees, basketball referees, golf referees, etc. In addition to referees, V4 Plus is suitable for daily training, construction sites, venue scheduling and other outdoor activities. | Large Battery Capacity: V4Plus headset runs on a 750mAh large rechargeable battery. With just 2 hours of charging, the intercom working time can reach 18hours and the standby time can reach 150hours, which can meet the needs of long-time referees communication. | Waterproof: With IP65 waterproof, the headset could handle almost all weather conditions. The Bluetooth headset can withstand 14℉ to 122℉ and can be used in most countries and regions.