Double Coated Breeds. Double coated dogs are found in all seven of the american kennel club pure breed groups. The topcoat is longer, and tends to grow slower than the undercoat.
Working dogs with double coats there are many working dog breeds that boast double coats some of which are incredibly fluffy which includes amongst others the pyrenean. The undercoat sheds and is released twice a year. When you start slacking in the grooming department, hairs in the undercoat will get caught up in the top coat, resulting in mats and tangles.