With multiple size Pet Bed Warmers available, it's now possible to add heat to most indoor pet beds. It slides into any zippered dog or cat bed and is recommended for beds with at least ½ inch of padding between the warmer and bed surface. Simply plug it in and the warmer will generate a subtle, comfortable heat that any pet is sure to enjoy. Please Note: This is a Pet Bed Warmer, it should only be used inside of a pet's bed and should never come in direct contact with your pet. Thermostatically Controlled Temperature Internal thermostats automatically adjust the Pet Bed Warmer's temperature as needed to create a comfortable resting area for dogs and cats. They're pre-set to heat to your pet's natural 102°F body temperature when he/she lies on the pad. When plugged in but not in use, the Pet Bed Warmer will maintain a temperature 10-15°F greater than the ambient room temperature. The Pet Bed Warmer is the essence of simplicity and has no on/off switch to monitor. Plug it in and the product will begin to warm automatically. Its soothing, gentle heat will not exceed the natural body temperature of a dog or cat, allowing your pet to enjoy hours of warmth. Multiple Size Options We've expanded the Pet Bed Warmer lineup to accommodate the needs of dogs and cats of all sizes. Now you can select the size that fits your pet's bed most closely. Small – 8.5" x 8.5" Medium – 5.5" x 20" Large – 11" x 23" X-Large – 15.5" x 26"