Because of its large size, the Standard can be applied to larger areas of the body, including the entire spine, both shoulders, and the legs. Versatility makes this the most popular size. Manual switch for safety. This means that you have to hold down the switch to keep the unit on. When you let go, the unit turns off. This is to ensure that you don't fall asleep with the unit on - to prevent burning. Product Size/Type: Large / Standard Product Dimensions: 14" X 27" Recommendations-Dosage/Usage: 15 to 20 minutes at a time Indications: Warnings: Danger: Carefully examine before each use. Discard unit if shows signs of deterioration. Follow instructions packed with unit. Do not use on infants, persons with poor circulation or insensitive skin. Persons with diabetes should be especially careful applying heat. Check skin frequently to avoid burns. Temperature is sufficiently intense to cause burns. Use no pins. Do not wet. Directions: To be comfortable, place a pillow under your ankles. If your chest is slightly hunched you may be more comfortable with a pillow under it. If you are sway backed you may prefer a pillow under your stomach. Included: Flannel Cover Max Temperature: Up to 180 Degrees Fahrenheit (Unit only has one temperature setting). Electrical Specs: 110 Volts; 150 Watts - 60 HZ A.C. - Cord is 6' in length