Since Eartecs UltraLITE headsets feature a self contained, "All in One" design, all the electronics including the battery, are installed right in the headset. The batteries are lightweight and are about the size of a book of matches. They charge in about 3 hours, run for 6 hours, and can be changed out in seconds. Since they are Li-ion, the batteries do not have to be "drained" after each use, and will never develop "battery memory". UltraLITE are breakthrough full duplex wireless headsets that provide hands-free, two-way voice communications. At the heart of these systems is a specialty "Master" headset that relays the digital signals generated by up to Six "Remote" units. The resulting open line talking pattern allows up to 7 people to talk simultaneously without pushing buttons. To formulate your standard UltraLITE system select any combination of Double or Single ear headsets - up to 7 units. All UltraLITE headsets are powered by a Lithium Polymer battery that will operate 6 hours when fully charged. Hands-Free, Open Line Talking Pattern for up to 6 wireless and 1 plug in headset.