811 Size: Large (13" x 13") Features: -Heating pad.-Versatile 13" x 13" unit has durable.-Help shape smoothly against painful joints, or the neck, jaw or sinus area for uniform comfort.-Hand held switch will shut off for safety if the user dozes off.-Produces moisture from the atmosphere.-Lets you add moisture if the atmospheric moisture is inadequate.-Made in the USA. Construction: -Lightly-weighted fabric construction.