Why "Warmawear"? *"Warmawear" insoles come with a extra-long 75cm lead from the battery back to the insole, which means you can use them with ski boots. Most heated insoles do not have long enough leads for use with ski boots.*With "Warmawear" insoles, the heating element runs down the whole length of the foot: most other insoles will only supply heat to the toe area. *Perfect for ski boots (75cm lead to battery). * Easy to cut to size: from US size 6 to US size 10 * Heating element runs down the whole length of the foot * Easy to move from one pair of shoes or boots to another pair. * 3 hour battery life with Duracell (effective life will be much longer because you"ll only need to leave the insoles on for short bursts) * 3 AA batteries per insole.Which size?Available in one size which can be cut down to fit almost any size shoe or boot, but should work well with any size between US size 6 to US size 10As a rough guide to help you to decide which size you need, there are lines marked out on the insoles. We recommend cutting them down gradually- bit by bit to achieve the best fit. How do they work? The insoles feature an advanced battery operated heating system, which circulates gentle warmth around the feet running down the whole length of the foot including the toes - which are the areas most prone to the cold.Supplied with battery boxes and garters to attach to your leg. When switched on, they will heat your feet up quickly yet gently with over 3 hours of hot time from good quality batteries. This time can be dramatically increased if you only have them switched on for short bursts.Each battery pack requires 3 standard or rechargeable "AA" battery"s for each side . Rechargeable batteries will be fine, but we recommend you go for the higher rated ones (2400mah +).