The Labrador Retriever, Labrador or just Lab, is a medium-large breed of retriever-gun dog. The Labrador is the most popular breed of dog in many nations. A favourite disability assistance breed in many countries, Labradors are frequently trained to aid those with blindness or autism, act as a therapy dog, or perform screening and detection work for law enforcement and other official agencies. The breed is best known for their obedience, loyalty, and playful composure. Additionally, they are prized as sporting and hunting dogs. The dogs Buccleuch Avon and Buccleuch Ned, given by Malmesbury to Buccleuch, were mated with bitches carrying blood from those originally imported by the 5th Duke and the 10th Earl of Home. The offspring are considered to be the ancestors of modern Labradors. Labradors are a medium-large breed, with males typically weighing 29–36 kg (65–80 lb) and females 25–32 kg (55–70 lb). The majority of the characteristics of this breed, with the exception of colour, are the result of breeding to produce a working retriever.