There are two main o-ring sizing types: standard and metric. Standard was developed for use in the United States, while the international community uses metric sizes. The metric sizes are further broken down by region, notably Europe and Japan.
Standard Sizes AS568
O-Rings are specified by three characteristics:
SIZE: Standard size are specified by their AS568 dash number. Non-standards are referenced by ID and CS.
HARDNESS: This is specified by a two-digit Shore A durometer number, ranging from 40(soft) to 90(hard), depending on the type of elastomer. Our standard durometer is 70 Shore A, except for Viton which is 75 Shore A. Standard durometer tolerance is ±5.
MATERIAL: Our standard range of materials is designated by ASTM abbreviation for each elastomer. Please refer to our Material Selection Guide for help with the rubber material selection process.