The English Mastiff is a breed of large dog. National kennel clubs, including the United Kingdom's Kennel Club and the American Kennel Club, refer to the breed as simply the Mastiff. Long haired Mastiffs, known as 'Fluffies', are caused by a recessive gene—they are occasionally seen. The AKC considers a long coat a fault but not cause for disqualification. English Mastiff colours are apricot-fawn, silver-fawn, fawn, or dark fawn-brindle, always with black on the muzzle, ears, and nose and around the eyes. . The genetic basis for the variability of coat in dogs has been much studied, but all the issues have not yet been resolved. The possible combination of homozygous brown and homozygous blue is a pale brown referred to as isabella in breeds where it is relatively common. . The greatest weight ever recorded for a dog, 343 pounds (155.6 kg), was that of an English Mastiff.