CertainTeed Landmark 3-tab shingles are a type of roofing shingle offered by CertainTeed. Unlike the XT25, which is a dimensional shingle, Landmark 3-tab shingles have a more traditional flat appearance. CertainTeed Landmark 3-tab shingles are designed to provide reliable performance and durability for residential roofs. They feature a fiberglass mat construction with an asphalt coating and mineral granules on the surface. These shingles are available in a variety of colors and are known for their classic and clean look.