Viton® (FKM) O-Rings

What FKM is, and whether Viton is the same thing

FKM is the ASTM D1418 designation for fluoroelastomers, the family of fluorine-containing rubbers used where a seal meets oil, fuel or solvent at elevated temperature. Viton is a polymer trademark owned by The Chemours Company; a molder buys the raw polymer and compounds it, so "genuine Viton" on a print fixes where the polymer came from, not who made the ring. A print that says FKM accepts any qualified fluoroelastomer compound. FPM is the same material in older European usage, and FFKM (perfluoroelastomer) is a separate, costlier family covered on the FFKM page.

FKM grades by designation

The letters after the trade name are the polymer maker's grade families (Chemours' Viton selection guide, read 2026-09-27). They differ in monomer mix, fluorine content and cure system; the compound datasheet names the grade, while most prints name only FKM and a hardness, or an AMS document. The temperature figures below are the Parker O-Ring Handbook (ORD 5700) family range, and a grade's own datasheet governs.

Grade descriptions are qualitative and follow the polymer maker's nomenclature; they are not a compatibility rating. The chemical compatibility guide covers the media, and the quote names the compound your print or your engineering specifies and sends its datasheet.

Viton O-ring specifications

Military and AMS callouts that specify FKM

Aerospace and OEM prints rarely say "Viton"; they name a material document, and the document status matters because the military originals are cancelled while parts are still ordered by the old numbers. The mil-spec O-rings by designator page gives the current document for each family. The statuses below are read from the DLA ASSIST and SAE Mobilus records (read 2026-09-24 to 2026-09-27).

The dash number after the slash sheet is the AS568 size, so an M83248/1-214 is a fluoroelastomer ring in size -214: the AS568 size chart carries the dimensions, and the M83248, AMS7276 and AMS7280 guides decode the documents. Where one of these documents has a qualified products list, the part comes from a manufacturer on it; Conquest supplies it with the certificate of conformance and, where the order calls for it, AS9102 first-article documentation.

Where Viton O-rings work, and where they fail

Sizes and forms we supply

Every AS568 size, the general-purpose dash sizes and the boss-seal sizes alike, and the ISO 3601 metric series, in the durometers listed above; O-ring cord for rings spliced and vulcanized by the maker in odd diameters (static service only); and X-rings and backup rings in the same families. The AS568 chart and the AS568 sizes in millimeters carry the dimensions, and the dash number guide explains the numbering.

How FKM compares with its neighbors

Where Viton fits

Where the medium is petroleum-based or chemically aggressive and the temperature exceeds what nitrile handles; the nitrile vs FKM comparison draws that line. The same polymer in sheet form is on the Viton (FKM) gaskets page. For steam or brake fluid, EPDM (see EPDM vs FKM); for dry heat with no oil, or extreme cold, silicone (see FKM vs silicone); for fuel in the cold, fluorosilicone (see fluorosilicone vs FKM); for ketones, amines and the most aggressive streams, FFKM (see FFKM vs FKM). A specification's temperature limit is a test condition, not an operating limit; the compound datasheet governs. A certificate of conformance ships with every order; the cure date is on the label, and the shelf-life guide explains how both are read.

Orders are handled under Conquest Seal's AS9100D quality management system, whose certificate scope includes distribution.

Sources: Parker O-Ring Handbook ORD 5700, section 2.2, read 2026-09-14; Chemours, Viton Fluoroelastomers Selection Guide C-11021 (9/19), page 1: about 3,000 hours at 232 C (450 F), a time-limited service limit, read 2026-09-27; Parker O-Ring Handbook ORD 5700, hardness guidance (page 2-10), stock O-ring kits (page 3-6) and Tables 8-4 and 8-5, read 2026-09-24 and 2026-09-25; ASTM D1418; AS568; AS568 size count, 369 sizes (349 general-purpose plus 20 boss): Parker O-Ring Handbook ORD 5700, section IX size tables (Series 2-XXX and the 3-9XX boss table), read 2026-09-27; ISO 3601; DLA ASSIST document details for MIL-R-83248, MIL-R-83248/1, MIL-R-83248/2, SAE-AMS7276, SAE-AMS7259 and SAE-AS83248/1 (read 2026-09-24 and 2026-09-25), and the MIL-R-83248/1A cancellation notice (Notice 5, 2008-07-24), read 2026-09-29; SAE Mobilus pages for AMS7287, AMS-R-83248, AS83248/1, AS3208, AS3209, AS3581 (read 2026-09-24; current-revision records for AMS7287, AS83248/1, AS3208, AS3209 and AS3581 read 2026-09-27); Chemours, Viton Fluoroelastomers Selection Guide (C-11021), families and cure systems, read 2026-09-27; SAE Mobilus current-revision record for AMS7280F (cancelled January 1992), read 2026-09-27.

Parker is a trademark of Parker Hannifin Corporation. Viton is a trademark of The Chemours Company; Aflas is a trademark of AGC. No affiliation or endorsement is implied.