9 11.5 Inch (Mens)/10.5 13 Inch (Womens) * Uses high tech wireless thermal technology no wires, extension cords, Velcro Straps or battery strap brackets & no batteries mounted to your ankle, shoe or waist. * Lithium ion polymer batteries embedded in the foot warmer insoles are rechargeable * Adjustable to three temperature settings to warm cold feet by remote control: settings are no heat, medium 100 degees & high 111 degrees * can be recharged up to 500 times using the charger that is included