Also known as Tetraseals® or lathe-cut rings, square rings are circular sealing devices that utilize square rather than round cross-sections. Available in many elastomeric compounds, square rings are used primarily in static applications. In larger diameters (above 2"), square rings often cost less than O-rings. Keep in mind, however, that O-rings generally provide a more positive seal because the circular cross-sections allow for more concentrated unit loading. Figure 140 illustrates the cross-section of a square ring.