Self-heating is a slightly misleading name for a genuinely useful thing. There is no element, no cable and nothing to plug in or remember to switch off. The mat works by returning an animal's own body heat rather than letting it drain away into a cold floor, which means there is nothing to chew through, nothing to overheat and no reason to think twice about leaving a dog on it while you are out of the house.

It is polyester fibre throughout and machine washable, which matters for a bed that lives on a hard floor and collects hair, and the underside is made to grip rather than slide when a dog stands up on it. Three sizes are made. The largest at 75 x 115cm is a crate-floor size for a big dog, the middle one suits most dogs curled, and the smallest is a cat-on-the-windowsill size or a puppy bed.

• S: 40 x 50cm
• M: 50 x 70cm
• L: 75 x 115cm
• Polyester fibre, machine washable
• Two colours: light grey and dark grey
• No power, batteries or cable required
• Non-slip underside

What it will not do. It cannot warm a pet who is not lying on it, and it cannot warm a cold or unwell animal back up, because it only conserves heat that is already there. Give it a few minutes to come up to temperature, and put it where your pet already chooses to sleep rather than where you would prefer them to. For an elderly or ill animal, treat it as a supplement to a warm room, not a replacement for one.

What the options mean. Sold in sizes from 40X50CM to 75X115CM — £10.99 to £11.99.

Who it's for: older dogs and cats who feel a cold floor through their joints, crate-trained dogs, thin-coated breeds, and anyone who does not want a heated pad and a cable near a chewer.