Blind disk is formally known as Flange cover, sometimes also referred to as Blind Flange or Pipe Plug. It is a type of flange without a hole, used for sealing pipe openings. It serves the same function as a cap or pipe end, but the blind disk is a removable sealing device, whereas the cap's seal is not intended to be opened again. There are various types of sealing surfaces, including flat, convex, concave, tenon and groove, and annular connection surfaces. Materials include carbon steel, stainless steel, alloy steel, copper, aluminum, PVC, and PPR.