There is no plug, no element and no battery here, and that is worth saying first, because the phrase self-heating does a great deal of work in a product title. What this actually does is reflect the heat your dog is already producing back into the blanket instead of letting it drain away into a cold floor. Lie on it and it warms in a few minutes. Get off it and it goes cold again.

That is a real mechanism rather than a trick, which is why the material matters. A dense plush pile traps a layer of still air and holds it against the dog, and the reflective inner layer stops that warmth disappearing downwards into tile or laminate. It works best where the cold is coming from underneath, so a kitchen floor, a car boot or a crate tray, and least well thrown over the top of a dog in a genuinely cold room.

• Plush pile with a heat-reflective inner layer
• Manufacturer's listed sizes: 60 x 45, 46 x 48, 89 x 56, 101 x 71 and 120 x 76cm
• Three colours: yellow, milky white and grey
• No power, batteries or heating element required
• Supplied as one blanket

The size labels do not line up. The manufacturer lists four size names, S through to XL, but five sets of measurements, and never says which belongs to which. Nothing here warms a cold room on its own: an arthritic dog in an unheated space needs the room heated, not just the bedding.

Who it's for: Dogs who sleep on tiles, laminate or in the back of the car, short-coated breeds who feel the cold, and anyone who does not want a mains cable anywhere near a chewer.