KTS® Cold Laser Therapy Device for Muscle Reliever(Premium Version)Portable & Convenient Operation: Small size and handheld, specially design for household use. 4 unit light with 808nm and 12 unit light with 650nm . The output power is 660Mw. One long press to turn on, press again to start treatment. A rechargeable 2600mAh lithium battery inside, when fully charged for 2 hours, its duration time reach 4 days. The 808 nm is a very weak beam, it is not as bright as the 650 nm, so the naked eye is difficult to observe