O-rings

Of the multitude of different O-Ring dimension standards in existence, the most popular in the United States is AS568. Formerly known as ARP 568, and currently maintained by the Society of Automotive Engineers, AS568 lists 369 sizes of O-Rings with corresponding dimensions and tolerances. This standard offers O-Rings in five different cross-sections, with inside diameters ranging from 132" to 26". Tube fitting boss seals are included in AS568 as "-900" series O-Ring sizes, and are intended for use in MS33649 (now superseded by SAE-AS5202) straight thread tube fittings.