Domestic Long Hair isn't a breed. It's the label used for a mixed-ancestry cat with a long coat, the fluffy counterpart of the Domestic Short Hair. These cats come from the general cat population, so they appear in every color and pattern, from tabby and calico to solid black, smoke and bicolor. Some resemble a Maine Coon or a Persian without sharing that ancestry.
With no breed standard, size, coat texture and personality differ from cat to cat. Most adults weigh 8 to 15 pounds, and the long fur can make them look even bigger. What they share is a coat that needs regular brushing to prevent mats and hairballs. In San Luis Obispo, where the hills dry out by summer, that routine also gives you a regular chance to check the fur for burrs and grass seeds.