HD closures and frontals are hairpieces that are used to cover the front hairline and provide a natural-looking finish to a sew-in or wig installation. They are called "HD" because they are made with a high-definition lace material that blends seamlessly with the skin. HD closures are small hairpieces that cover only the front hairline. They are typically 4 inches by 4 inches in size and can be used to create a part in the hair. HD frontals, on the other hand, are larger hairpieces that cover the entire front hairline, from ear to ear. They can be used to create a natural-looking hairline, as well as a part.