A Square-Ring is a sealing device made in the form of a torus (round top view), with a square shaped cross-section (side view), also called Washer Rings, Lathe-Cut Rings, TetraSeal.
The primary reason for using a Square-ring in a sealing application is that they perform the sealing function in a superior manner – and at a cost lower than any other comparable sealing device. For existing applications, there is no need to change the design or procedures. Square-rings fit in O-ring grooves and are interchangeable size for size.
Square rings are available in a variety of rubber and plastic materials such as NBR, Viton, EPDM, Teflon, etc. In most static applications, a square ring will serve as a direct replacement for an O-ring and generally will perform a high pressure sealing function as well as or better than an O-ring.