Flange protectors are designed to protect flanges from damage during shipping, or from exposure to corrosive elements. These products are usually made of plastic, polyvinyl chloride (PVC), silicone, or vinyl. Some suppliers group flange protectors with caps, closures, grips, inserts, plugs, stoppers, and other devices for piping and tubing. Other suppliers list their products separately, and designate them as suitable for either pipe flange protection or tube flange protection. Product specifications for flange protectors include material of construction, method of attachment, and type or style. Most flange protectors are designed to be bolted, clipped, or pushed into place. Some push-on products are designed to work with adhesives. Flange protectors may have a raised face or a full face, and may be listed as disks or covers. Features for flange protectors include quick-fit attachments and suitability for high-pressure service. Material of construction is an important parameter to consider when selecting flange protectors. Plastic flange protectors are usually made of thermoplastics such as low-density polyethylene (LDPE) and high-density polyethyelene. LDPE provides excellent resistance to acids, alcohols, bases and esters. HDPE resists a variety of solvents and is used in many commercial applications. PVC flange protectors are made of polyvinyl chloride (PVC), a biologically and chemically-resistant thermoplastic polymer that is used widely in food processing and water transport applications. Silicone flange protectors are valued for the thermal stability and water repellence that silicone imparts. Vinyl flange protectors include products made from PVC, as well as flange protectors made from polyvinyl acetate (PVAc) and polyvinyl alcohol (PVA). There are many different types of flange protectors. Examples include bolted quick-fit flange covers, SAE high-pressure flange covers, and push-in flange covers. Bolted quick-fit flange covers do not require fasteners and are designed to fit flange bolt holes. SAE high-pressure flange covers do not require fasteners either, and are approved for high-pressure service by the Society of Automotive Engineers (SAE). Push-in flange covers have flexible fins to ensure a tight fit in the bore hole. Flange protection products such as integral arrow-clip flange disks, full-face flange covers, raised-face flange plugs, full-face flange disks, and raised-face flange disks are also available.