SAE J1453 · ISO 8434-3

O-ring face seal, ORFS (SAE J1453 / ISO 8434-3)

A straight Unified inch thread with a flat face and an O-ring in a groove on the male nose. The most leak-resistant of the common hydraulic connections.

8 sizes60 degree flanksParallel threadO-ring face seal (flat face)

Identify a fitting Compare with a lookalike

Schematic cross-section of the male half, upper side only, with the centre line dashed and the open end on the left. Cone angles are drawn at their true angle from the axis; nothing else is to scale and no dimension should be measured off it.

How to recognise it

A completely flat male nose with a shallow O-ring groove machined into the face, and a flat female face with no groove at all.

Where it seals: The O-ring squashed between the two flat faces. The thread only holds the load.

Missing or pinched O-rings are the only common failure on this connection. The male face must be clean and undamaged; a nick across the groove will weep no matter how hard the nut is pulled up.

How it is sized

Sized by dash number for the tube outside diameter, but the thread is larger than the JIC thread of the same dash.

Where you will find it: High pressure and vibration-heavy hydraulics, mobile equipment, anywhere a leak is expensive.

Also searched as: ORFS, O-ring face seal, flat face O-ring, FFOR.

All sizes

ORFS (O-ring face seal) size table

Thread, pitch, diameters and working pressure for every ORFS (O-ring face seal) size in the database.
Size	Thread	TPI / pitch	Basic major Ø	Measured across crests	Tube / trade size	Working pressure
-04 ORFS	9/16-18 UNF	18 TPI (1.411 mm pitch)	14.29 mm / 0.563 in	14.1 mm to 14.22 mm	0.25 in	6,000 psi (414 bar)
-06 ORFS	11/16-16 UNF	16 TPI (1.587 mm pitch)	17.46 mm / 0.688 in	17.3 mm to 17.53 mm	0.375 in	6,000 psi (414 bar)
-08 ORFS	13/16-16 UNF	16 TPI (1.587 mm pitch)	20.64 mm / 0.813 in	20.6 mm to 20.83 mm	0.5 in	6,000 psi (414 bar)
-10 ORFS	1-14 UNF	14 TPI (1.814 mm pitch)	25.4 mm / 1 in	25.3 mm to 25.4 mm	0.625 in	6,000 psi (414 bar)
-12 ORFS	1 3/16-12 UN	12 TPI (2.117 mm pitch)	30.16 mm / 1.188 in	30 mm to 30.23 mm	0.75 in	6,000 psi (414 bar)
-16 ORFS	1 7/16-12 UN	12 TPI (2.117 mm pitch)	36.51 mm / 1.438 in	36.3 mm to 36.58 mm	1 in	5,000 to 6,000 psi (345 to 414 bar)
-20 ORFS	1 11/16-12 UN	12 TPI (2.117 mm pitch)	42.86 mm / 1.688 in	42.6 mm to 42.93 mm	1.25 in	4,000 psi (276 bar)
-24 ORFS	2-12 UN	12 TPI (2.117 mm pitch)	50.8 mm / 2 in	50.6 mm to 50.8 mm	1.5 in	3,000 to 4,000 psi (207 to 276 bar)

8 of the 8 sizes carry a published working pressure. Every one of them prints the exact conditions it applies under on its own page - a figure without its material and safety factor is not a rating.

On paper

Identification sheets covering ORFS (O-ring face seal)

SAE inch fittings: JIC 37, ORB, ORFS and SAE 454 sections Seat and thread identification: all ten standards1 sections Published working pressures, with the conditions they apply under5 sections

Where these figures come from

Dimensions are as defined by SAE J1453, ISO 8434-3. FittingKey is an independent reference and is not affiliated with, endorsed by or approved by any standards body or fitting manufacturer.

Every value on this page was checked against 7 independent published sources:

Fluid Ports and Connectors Identification Guide - McGill Hose & Coupling, SAE J512, J514, J1453, J1926-1, ISO 228, ISO 7, DIN 2353, JIS (distributor, read 2026-08-27)
Master catalogue: conformance, working pressure and torque tables - Tompkins Industries, SAE J514, SAE J1453, SAE J1926-1, SAE J1926-3, ISO 11926-1 (manufacturer, read 2026-08-27)
Catalogue page 4: SAE J514 working pressure ratings, and SAE J1453 working, proof and minimum burst pressures for face seal fittings - Brennan Industries, SAE J514, SAE J1453 (manufacturer, read 2026-08-27)
Thread identification: BSP, JIC, ORFS and metric tables - Apex Fluid Power, ISO 12151-2, ISO 8434-1 (distributor, read 2026-08-27)
Thread identification guide, O-ring face seal, with adapter sizing chart - Central Hydraulic Supply, SAE J1453 (distributor, read 2026-08-27)
Boss, face and flange O-rings: AS568 900 series and zero series - Global O-Ring and Seal, AS568 (manufacturer, read 2026-08-27)
ORFS fitting thread sizes - GageRef, SAE J1453 (reference table, read 2026-08-27)

Which published source supplied each column, and what it gave.
Column	Sources	What they gave
Dash and trade size	tompkins, mcgill-id, gageref-orfs, chs-orfs	Four publishers agree the series runs -04 to -24. One adds a -14 and a -32 that no other source carries; both are recorded as gaps rather than published.
Basic major diameter	tompkins, mcgill-id	The thread designation fixes the basic major diameter: a 3/4-16 UNF thread has a basic major diameter of 0.750 in, which is 19.05 mm at 1 in = 25.4 mm exactly. The inch and millimetre columns are that one figure in two units.
Measured male thread diameter	apex-threadid, mcgill-id	Two identification charts. A third prints 22.0 mm at -08, which fits neither the thread nor its own female figure, and is recorded as a disagreement instead of being averaged in.
O-ring size	globaloring, chs-orfs	The AS568 zero-series dash numbers are identical in both: 011, 012, 014, 016, 018, 021, 025 and 029.
Working pressure	tompkins, brennan-pressure	Two catalogues, steel, 4 to 1 against minimum burst per SAE J1453, straight and adjustable studs given separately. Both pairs match on all eight sizes.

Sources disagree: ORFS -08 male thread diameter.

22.0 mm (gates-idchart)
20.6 mm (apex-threadid)
20.8 mm (mcgill-id)

22.0 mm cannot be a 13/16 in thread, whose basic major diameter is 20.64 mm, and the same chart gives a female inside diameter of 19.1 mm, which only fits the smaller figure. The outlier is treated as a misprint and excluded from the published span, and it is recorded here so nobody has to work that out twice.