Solid elastomeric rings are compression seals that are used to prevent the leakage of fluid or air. They are made of flexible, elastomeric materials and are capable of repeated contraction and expansion without excessive wear and tear. There are many types of solid elastomeric rings. Examples include X-rings or multiple rings, rectangular rings, tetraseals, trapezoid rings, T-section rings, delta rings, D-rings, heart rings, H-rings, and diamond rings. Most elastomeric rings are fitted to a groove that holds them tightly and securely in place between two surfaces. Products such as rubber rings need to fit securely to take up any clearance that may be present. Typically, the properties of advanced elastomers allow solid elastomeric rings to return to their previous or original shape when pressure is released.