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.