Adjustable to any windowsill using provided Velcro fasteners. Screws are provided for more permanent attachment # Supports over 40 pounds # 6 Watt Advanced Heat Dispersion heater # Warms up only when pet is on the sill # Internal dual thermostats keep the temperature at a comfortable 102° when in use. When not in use the surface of the bed will remain 12° to 15° above ambient air (room) temperature…# Super soft orthopedic foam # Washable faux lambskin