A flange is an external or internal rim added for strength. The flange fits between two matching components to form an airtight seal and to prevent the two components from forging to one another or creating friction between them. Although the term flange usually refers to the actual raised rim or lip of a fitting, many flanged fittings are also known as 'flanges'. The term "flange" is also used when describing the tool used to make flanges. By using flanges, pipes can be assembled or disassembled very easily.

Flanges are divided into "pressure classes” which allows flanges to take different pressure ratings. ANSI numbers refer to the class of flange and these "pressure classes" also have various pressure and temperature ratings depending on the different materials that are used.

The flange faces are made to industry type dimensions and are characteristically "flat face", "raised face", "tongue and groove", or "ring joint" styles of flange. Typical flange designs are "welding neck", "slip-on", "boss", "lap joint", "socket weld", "threaded", and also "blind". A gate valve, also known as a sluice valve usually has flanged ends which are drilled.

Other examples of valves with flanged seals include:

• Wafer Pattern ball Valve stainless steel and carbon steel wafer pattern ball valve with lever handle.
• Flanged Ball Valve two piece stainless steel and carbon steel ball valve with lever handle.
• Wafer Type butterfly Valve Stainless Steel Disc.
• Cast iron universal wafer type butterfly valve.
• Lug Type butterfly Valve Stainless Steel.
• Lug Type butterfly Valve Stainless Cast Iron.