O-Ring Part Number Cross-Reference

The two halves of an O-ring callout

Every O-ring callout carries a size and a material, and they cross to another supplier by different rules. The table splits six common callouts into those two halves. The document statuses are the ones on this site's mil-spec O-ring index, read from the DLA ASSIST and SAE records.

The same dash number in five mil-spec callouts is one size in several materials, which is why a size match alone never settles a cross.

Crossing a part number, step by step

1. Split the callout into its prefix, its three-digit dash number and its material suffix (a compound code, a slash sheet or a specification).
2. Check the dash number against the AS568 size chart. A number that falls in one of the gaps in the numbering (the dash number guide lists them) is not an AS568 size, and the ring has to be crossed by its inside diameter and cross-section instead (how to measure an O-ring).
3. Resolve the prefix. On the 2- series the prefix only says the size is AS568; the 2-series chart lists every size with its metric dimensions.
4. Resolve the material. A military or SAE callout already names its document. A maker's compound code does not, so read the maker's compound sheet or handbook for the document it is made to, if any.
5. Decide what the new part has to meet. If the print names a specification, the new part is quoted to that document; if it names only a brand's compound, the substitute needs the print owner's approval.

Does a 2-214 cross to a mil-spec part number?

The size does: MS28775-214, M83461/1-214, M83248/1-214, AS3209-214 and M25988/1-214 are all the -214 size. The material does not follow on its own. A commercial nitrile ring in the -214 size is not an MS28775-214 unless it is made to MIL-PRF-25732 by a manufacturer qualified to that document and certified that way. The Parker O-Ring Handbook's specification tables pair that maker's compound numbers with the military and AMS documents they are made to, which is the published place to check a compound code against a document. Going the other way, whether a mil-spec ring may replace a commercial one on your print is also the print owner's decision.

What "or equal" means on a print, and who decides

On an engineering drawing the decision belongs to the design activity, the organization that holds responsibility for the design and therefore the authority to change it, in the sense ASME Y14.100 gives the term. In a federal solicitation, FAR 52.211-6 Brand Name or Equal says an "equal" offer must meet the salient physical, functional or performance characteristics the solicitation lists, must name the brand and model offered, and must include descriptive literature; the contracting officer then evaluates it. Either way the supplier furnishes the evidence and the buyer's side makes the call. Conquest quotes the equal you approve, sends the maker's sheet with the quote, and never decides equivalence for you. The FFKM brands and grades cross-reference shows the same rule applied to perfluoroelastomer grades.

What the online cross-reference tools do

Parker publishes a cross-reference tool that takes another maker's part number, or an obsolete Parker number, and returns the Parker product it lists as equivalent. A tool like that answers the size and names one maker's suggested product. It does not approve an equal for your print, and it does not tell you whether the suggested compound is qualified to the document your drawing names. Treat its answer as a starting point for the specification check above.

What to send for a quote by part number

• The callout exactly as the print or the old purchase order reads, with the drawing revision
• The quantity
• The specification and its revision, if the print names one
• Whether an equal is allowed, and which one your engineering has approved
• The paperwork you need: a certificate of conformance ships with every order; say if you also need the manufacturer's certificate, a test report, AS9102 first-article documentation or a QPL source
• Any age limit counted from the cure date (shelf-life guide)

Put it in the quote form. We stock every AS568 size, and a person replies within one business day.

Parker is a trademark of Parker Hannifin Corporation. No affiliation or endorsement is implied.

Sources

1. SAE AS568F, Aerospace Size Standard for O-rings (SAE Mobilus record, title and revision only, read 2026-09-06); dash numbers only, no table reproduced
2. DLA ASSIST document records for MIL-PRF-25732, MIL-DTL-25988/1 and MIL-R-83248/1, and SAE Mobilus records for AS83248/1, AS3209 and AMS7276, as read for this site's mil-spec register (read 2026-09-06 and 2026-09-13)
3. Parker O-Ring Handbook ORD 5700 (2018): the 2- series size prefix and the specification-to-compound tables of section 8; nothing reproduced
4. FAR 52.211-6, Brand Name or Equal (Aug 1999), and FAR 11.104, acquisition.gov, read 2026-09-24
5. ASME Y14.100, Engineering Drawing Practices: the design activity definition as quoted in NASA KSC-GP-435 Volume I, Revision H, Engineering Drawing Practices (NASA Technical Reports Server), read 2026-09-24
6. Parker Hannifin, Cross Reference tool description (discover.parker.com/crossreference), read 2026-09-24