Domestic Long Hair is a coat description, not a pedigreed breed. It's the label given to mixed-ancestry cats with medium-to-long fur, and they come 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. Adults usually weigh 8 to 15 pounds, though the fluff makes many look bigger.
Because there's no breed standard, size, coat texture and personality vary a lot from cat to cat. What they share is a coat that needs regular brushing to prevent mats and hairballs, plus the genetic diversity that tends to keep mixed cats sturdy. In St. Peters, that routine fits easily into indoor life, and spending time with a cat before you decide will tell you more than the label does.