An O-ring is a solid-rubber seal shaped like a doughnut or torus.  When pressed between mating surfaces, an O-ring blocks the passage of liquids or gases.  Our o-rings are available in a wide range of standard sizes that are suitable for nearly all sealing applications.

Two dimensions define the size of an O-ring:  its inside diameter (ID) and its cross-sectional diameter (CS). 
(These dimensions are illustrated above.)