Therm-ic Basic Powerpack with Trim-fit heating elements. This can be your best choice because it is simple to use, easy to install and can be used world wide. The Basic Powerpack is also the least expensive option for those who only need heat occasionally. Therm-ic Basic features • Can be used world wide! • Fits every type of winter boot. • Impluse Control: The warmth is transferred from the battery pack to the heating element by impulses. • Advantages: Impulse heating elements deliver more energy. • Duration: Comfortable warmth up to 12 hours with fresh AA alkaline batteries (not included).Heat settings… You can select between 3 settings to determine the amount of heat you desire. • Setting 1: 35C/95F and lasts approximately 12 hours. • Setting 2: 42C/108F and lasts approximately 5.5 hours. • Setting 3: 68C/154F and lasts approximately 2 hours. Results are based on fresh AA Alkaline batteries. Expect about 20% less results if you use rechargeable batteries. Keep in mind, you dont have the heat on all the time. Only when you need it. For instance, you turn the batteries off when you go inside for lunch or if your feet are warm. Youll receive • Instructions on how to use. • 2 battery housings that hold 4- AA batteries each and clip to the back of your boot or shoes. • Battery specs- weight with 4 batteries- 5.3 ounces, size- 3 high x 2 3/4 wide x 1 deep. • 2 heating elements with connecting wires. • 2 TrimFit self-adhesive Cambrelle fabric covers to prevent your socks from catching the wires or heating elements when you slide your foot in or out of your boot. • A 1 year manufactures warranty.