The CRL SDK100ULBR Unlacquered Brass Traditional Style Back-to-Back Shower Door Knobs are designed for glass shower doors with a thickness between 1/4" and 1/2" (6 to 12 mm) and requiring a 3/8" or 1/2" (10 or 12 mm) diameter hole. They are suitable for various enclosure types including corner, niche, bathtub, and tailor-made solutions.