The Cairn Terrier has a harsh weather-resistant outer coat that can be black, cream, wheaten, red, sandy, gray, or brindled in any of these colors. Pure black, black and tan, and white are not permitted by many kennel clubs. While registration of white Cairns was once permitted, after 1917, the American Kennel Club required them to be registered as West Highland White Terriers. A notable characteristic of Cairns is that brindled Cairns frequently change colour throughout their lifetimes. It is not uncommon for a brindled Cairn to become progressively more black or silver as it ages. The Cairn is double-coated, with a soft, dense undercoat and a harsh outer coat. A well-groomed Cairn has a rough-and-ready appearance, free of artifice or exaggeration. The Cairn Terrier was registered into the American Kennel Club in 1903.