Viking Standard and Quick Response Concealed Pendent Sprinkler VK4621, K5.6 (80.6 metric), is a small thermosensitive, glass-bulb sprinkler designed for installation on concealed pipe systems where the appearance of a smooth ceiling is desired. The low-profile cover assemblies provide up to ½” (13 mm) of vertical adjustment. The integral threaded adapter cup accepts push-on or thread-on cover plates.