A small dog or puppy under 4kg is the trickiest weight bracket for flea treatment, because a lot of products are built around an adult dog's dosing and simply don't have a version scaled down far enough — which is exactly the gap this one is sized for.

It's a fast-acting spot-on containing imidacloprid, applied to the skin, and Johnson's say it kills fleas on contact on the dog and in the surrounding area, with up to two months of protection from the pack. It comes as two vials, each giving up to four weeks of cover, and it's specifically for dogs and puppies up to 4kg, over 8 weeks of age.

• 2 vials (2-treatment pack)
• Each vial gives up to 4 weeks of protection
• Kills fleas on contact, on the dog and the surrounding area
• Contains imidacloprid
• For dogs and puppies up to 4kg, over 8 weeks of age

On the weight limit. 4kg is the ceiling Johnson's give for this particular size, and going over it isn't a case of "close enough" — a dog that's grown past that weight, or a puppy you're not sure about, needs the correct size for their actual weight rather than this one stretched to cover it.

Who it's for: owners of a puppy or small adult dog under 4kg starting flea protection, who want two full treatments in one pack rather than buying single doses.