dr. prepare heated vest, unisex heated clothing for men women, lightweight usb electric heated jacket with 3 heating levels, 6 heating zones, adjustable size for hiking (battery pack not included) dr.prepare for a combination of functional comfort and quilted design, reach for the sleeveless quilted heated vest from dr. prepare, this unisex heated vest helps you stay cozy and warm. operation: ※ please use a portable battery pack (not included) with 2a or 2.4a usb output to power up this heated vest. ※ step 1. unzip the inner pocket and take out the usb cable. step 2. insert the usb cable into the usb output on the battery. then push the power button on your battery pack to turn it on. the thermal switch on the vest (near your chest) now cycles through red, blue, and green light for once, indicating the heated vest is plugged in. step 3. long press the thermal switch for 2 seconds and it will flash red light. the heated vest will enter the auto mode. in auto mode, the temperature of your heated vest will regulate from high to medium after the red light flashes for 5 minutes. step 4. if you prefer a certain heating level to the auto mode, short press the thermal switch. then you can adjust temperature settings from high, medium to low. the red light stands for high heat. the blue light indicates medium heat and the green light signals low heat. step 5. press and hold the thermal switch for 2 seconds to stop the heated vest from heating. specifications: name: heated vest input: 5v / 1.9a rated wattage: 9.5w outer shell: 100% polyester filling: 100% polyester three heating levels: 131°f (high, red light), 122°f (medium, blue light) 113°f (low, green light)