Engineering work needs to check dimensional standards, groove standards, material standards, appearance quality standards, and application conditions at the same time. Domestic hydraulic and pneumatic equipment usually prioritizes the GB/T 3452 series; international projects prioritize the ISO 3601 series; North American imported equipment, aerospace fasteners, SAE thread-fitting connections and similar scenarios prioritize the SAE AS568 dash number. GB/T 3452.1-2005 is marked as currently in force on the national standards information platform and shows it was revised from ISO 3601-1:2002; ISO 3601-1:2012 is the current ISO published version, and the page shows this standard was reconfirmed in 2022 and remains valid.

How Are the Standard Systems Different?

The SAE AS568F official page states this standard specifies O-ring internal diameters, cross-sections, tolerances and dimension identification dash numbers, and is used for sealing applications and straight thread tube fitting boss gaskets; AS568F was reaffirmed on 2026-01-29.

How to Use the GB/T 3452 Series

GB/T 3452 is not a single dimensional table, but a set of sub-part standards. In practice, it is recommended to be referenced as follows:

AS568 Dash Number: How to Read It

The AS568 dash number is a three-digit identification number, e.g. AS568-214 or written directly as -214. It is not a millimeter dimension, nor is it an internal-diameter value. Common AS568 cross-section series are as follows:

Global O-Ring's AS568 dimension table cross-references the series, inch cross-section, tolerance, and corresponding mm values listed above; Trelleborg's AS568 material reference also notes AS568's Class A dimension system corresponds to ISO 3601-1 Class A.

How to Select for Different Scenarios

Repairing imported equipment: prioritize the OEM manual, BOM, exploded diagram, or original-part markings. North American equipment and aerospace parts commonly use SAE AS568 dash numbers; European or international OEMs more often use ISO 3601, DIN ISO, or customer company standards. When replacing aged legacy parts, back-calculate from the actual part dimensions and groove dimensions rather than only referencing the standard.

Exporting products: if the customer drawing specifies AS568, quote by AS568 dash number; if the customer drawing specifies ISO 3601, quote by ISO dimension code. ISO 3601-2 has been published as the 2025 edition; its scope covers Class A O-ring general industrial installation dimensions and Class B O-rings for installation dimensions on specific inch-based hardware, as well as O-ring with/without back-up ring installation dimensions.

Domestic hydraulic/pneumatic equipment: for routine new designs, select dimensions per GB/T 3452.1, verify grooves per GB/T 3452.3, agree on appearance per GB/T 3452.2, and define material per GB/T 3452.5 or company material specifications. Purchase orders should fully state: standard number, ID, CS, material, hardness, color, appearance grade, quantity, whether back-up rings are needed, and inspection report requirements.

Purchasing Specification Templates

Domestic GB/T Notation:

O-ring, GB/T 3452.1-2005, ID 25.0 × CS 3.55 mm, NBR 70 Shore A, black, appearance per GB/T 3452.2, quantity 5,000 pcs.

International ISO Notation:

O-ring, ISO 3601-1, size code and tolerance class per drawing, ID × CS shown on drawing, FKM 75 Shore A, quality grade per ISO 3601-3, qty 2,000 pcs.

North American AS568 Notation:

O-ring, AS568-214, FKM 75 Shore A, color as specified, quality grade per ISO 3601-3 or customer drawing, qty 1,000 pcs.

Imported/Retrofit Equipment Inquiry Notation:

Equipment brand/model, legacy part photo, suspected dash number, measured ID/CS, media, temperature, pressure, installation location, annual usage — this way the supplier can determine whether it is GB/T, ISO, AS568, or a customer-specific part.