Dash Number 427 O-Rings | McMaster-Carr

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	Cross Section Shape Cross Section Shape


Round	Square

Rectangle	X

	System of Measurement System of Measurement

Inch

	ID ID

4.725"

4.801"

	OD OD

5.275"

	Dash Number Dash Number	Show

427

	Dash Number Dash Number	Hide

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	Width Width

0.236"

0.275"

	Fractional Width Fractional Width

1/4

	Material Material

Plastic

Rubber

	For Use With For Use With

	Color Color

	Black		Red
	White		Clear

	Hardness Hardness

	Hardness Rating Hardness Rating


Soft	Medium

Hard

	Fractional ID Fractional ID

4 3/4

	Fractional OD Fractional OD

5 1/4

	Maximum Temperature Maximum Temperature

	Minimum Temperature Minimum Temperature

-250° F or less

-99° to -50° F

-49° to 0° F

	DFARS (Defense Acquisition Regulations Supplement) DFARS (Defense Acquisition Regulations Supplement)

DFARS Specialty Metals
COTS-Exempt

	Specifications Met Specifications Met

	Thickness Thickness

0.117"

	Construction Construction

Solid

	Top Shape Top Shape

Contoured

	Core Material Core Material

Viton® Fluoroelastomer
Rubber

Silicone Rubber

	Core Color Core Color

	Black
	Red

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15 Products

About O-Rings

Made of Buna-N, these O-rings resist grease, hydraulic oil, and motor oil—plus mild chemicals and water. However, Buna-N is not for use with brake fluid. These O-rings are commonly used to create multidirectional seals between two parts in power transmission assemblies, hydraulic cylinders, and pneumatic cylinders. With a round profile, they resist compression and tearing to keep their shape over time, so they’re reusable. All have shelf life, cure date, and a traceable lot number printed on the bag. Many meet ASTM D2000 and SAE J200, international standards for rubber products.

Inch O-rings have a dash number and are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

Inch

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Hardness	Specifications Met	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 70A (Medium)	ASTM D2000, SAE AS568, SAE J200	-40° to 250°	Black	5	00000000	00000

Oil-Resistant Hard Buna-N O-Rings

Offering better wear resistance than standard Buna-N O-rings, these hard O-rings are also resilient and tear resistant. They resist grease, petroleum fluids, and motor oil. All have a round profile and are suitable for a wide range of static and dynamic sealing applications.

Inch O-rings have a dash number and are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

Inch

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Hardness	Specifications Met	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 90A (Hard)	ASTM D2000, SAE AS568, SAE J200	-30° to 250°	Black	10	00000000	000000

Square-Profile Oil-Resistant Buna-N O-Rings

With flat edges on all four sides, square-profile O-rings cover more surface than round-profile O-rings for a better seal in static applications, such as hose, pipe, and faucet connections. They’re made of Buna-N, which is resilient and offers excellent tear resistance. They resist hydraulic oils and motor oil.

Inch O-rings have a dash number and are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

Inch

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Hardness	Specifications Met	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 70A (Medium)	ASTM D2000, SAE AS568, SAE J200	-30° to 212°	Black	5	00000000	00000

X-Profile Oil-Resistant Buna-N O-Rings

Also known as Quattro Seals and X-rings, these X-profile O-rings have four points of contact for a better seal in dynamic applications than round-profile O-rings. They also require less compression to make a seal, so they offer a longer service life. These O-rings are made of Buna-N, which is resilient and tear resistant. They resist motor oil. These O-rings are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Hardness	Specifications Met	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 70A (Medium)	ASTM D2000, SAE AS568, SAE J200	-30° to 225°	Black	5	000000000	000000

Oil-Resistant Mil. Spec. Buna-N O-Rings

Choose these O-rings for their adherence to strict military standards for material and construction. Made of Buna-N, they are resilient and offer resistance to tearing, motor oil, ammonia, ethylene glycol, isopropyl alcohol, and mineral oil. These O-rings have a round profile and are suitable for a wide range of static and dynamic sealing applications. All are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Hardness	Specifications Met	Temp. Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 65A (Medium)	ASTM D2000, MIL-I-45208, SAE AS3578, SAE AS568, SAE J200	-20° to 250°	Black	2	00000000	000000

Oil- and Abrasion-Resistant Polyurethane O-Rings

More abrasion resistant than Buna-N O-rings, these polyurethane O-rings resist mineral oil, motor oil, and ethylene glycol. They have a round profile and are suitable for a wide range of static and dynamic sealing applications. All are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Hardness	Specifications Met	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 1/4 Fractional (0.275"Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 70A (Medium)	ASTM D2000, SAE AS568, SAE J200	-40° to 200°	Black	1	00000000	000000

Chemical-Resistant Viton® Fluoroelastomer O-Rings

These Viton® fluoroelastomer O-rings resist a wide range of chemicals, including benzene, butyl alcohol, and ethylene glycol. They have a round profile and are suitable for both static and dynamic sealing applications.

Inch O-rings have a dash number and are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

Inch

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Hardness	Specifications Met	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 75A (Medium)	ASTM D2000, SAE AS568, SAE J200	0° to 400°	Black	2	00000000	000000

X-Profile Chemical-Resistant Viton® Fluoroelastomer O-Rings

Also known as Quattro Seals and X-rings, these X-profile O-rings have four points of contact for a better seal in dynamic applications than round-profile O-rings. They also require less compression to make a seal, so they offer a longer service life. Made of Viton® fluoroelastomer, these O-rings resist a wide range of chemicals, including benzene, butyl alcohol, and ethylene glycol. All are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Hardness	Specifications Met	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 75A (Medium)	ASTM D2000, SAE AS568, SAE J200	-15° to 400°	Black	1	00000000	000000

Ultra-Chemical-Resistant Rigid PTFE O-Rings

Rigid and hard with a slippery surface, these PTFE O-rings resist harsh chemicals, such as acetone, fluorinated solvents, methanol, and boric acid. They have a round profile and are suitable for a wide range of static and dynamic sealing applications.

Inch O-rings have a dash number and are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

Inch

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Hardness	Specifications Met	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 55D (Hard)	FDA Compliant 21 CFR 177.1550, SAE AS568	-300° to 500°	White	1	00000000	000000

Ultra-Chemical-Resistant FEP-Encapsulated Viton® Fluoroelastomer O-Rings

If the FEP casing on these O-rings wears away, the Viton® fluoroelastomer core will continue to ward off chemicals. They are just as chemical resistant as PTFE O-rings, but the core is soft to make them more compressible. These O-rings resist acetone, solvents, methanol, and boric acid. They have a round profile and are suitable for a wide range of static and dynamic sealing applications. All are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Casing Hardness	Core Hardness	Specifications Met	Temperature Range, °F	Color		Each
Wd.:1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 55D (Hard)	Durometer 75A (Medium)	ASTM D2000, ASTM D2116, SAE AS568, SAE J200	-15° to 400°	Clear with Black Inner Ring	000000000	000000

Ultra-Chemical-Resistant FEP-Encapsulated Silicone O-Rings

The FEP casing on these O-rings provides the same level of resistance to harsh chemicals as PTFE O-rings, but the silicone core is soft to make these O-rings more compressible. They resist acetone, solvents, methanol, and boric acid. All have a round profile and are suitable for a wide range of static and dynamic sealing applications. These O-rings are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Casing Hardness	Core Hardness	Specifications Met	Temperature Range, °F	Color		Each
Wd.:1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 55D (Hard)	Durometer 70A (Medium)	ASTM D2000, FDA Compliant 21 CFR 177.1550, FDA Compliant 21 CFR 177.2600, SAE AS568, SAE J200	-75° to 400°	Clear with Red Inner Ring	00000000	000000

High-Temperature Soft Silicone O-Rings

Able to withstand temperatures up to 400° F, these silicone O-rings are softer than standard silicone O-rings for a better seal in low-pressure applications. They have a round profile and are suitable for a wide range of static and dynamic sealing applications. All are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Hardness	Specifications Met	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 50A (Soft)	ASTM D2000, SAE AS568	-60° to 400°	Red	1	00000000	00000

High-Temperature Silicone O-Rings

These silicone O-rings withstand temperatures up to 400° F or 450° F. They have a round profile and are suitable for a wide range of static and dynamic sealing applications. All have a cure date and a traceable lot number printed on the bag.

Inch O-rings have a dash number. USP VI Certified, they meet testing requirements for material quality.

For technical drawings and 3-D models, click on a part number.

Inch

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Hardness	Specifications Met	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 70A (Medium)	ASTM D2000, FDA Compliant 21 CFR 177.2600, SAE AS568, SAE J200, USP VI Certified	-60° to 400°	Red	5	00000000	000000

Water- and Steam-Resistant EPDM O-Rings

These EPDM O-rings resist water, steam, ethanol, and ethylene glycol. They have a round profile and are suitable for a wide range of static and dynamic sealing applications. All are sized to the SAE standard AS568.

For technical drawings and 3-D models, click on a part number.

	Fractional		Actual
Dash Number	ID	OD	ID	OD	Hardness	Specifications Met	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 1/4 Fractional (0.275" Actual)
427	4 3/4	5 1/4	4.725"	5.275"	Durometer 70A (Medium)	ASTM D2000, SAE AS568, SAE J200	-70° to 250°	Black	5	00000000	00000

Oil-Resistant Buna-N Backup Rings

Made of Buna-N, these backup rings resist grease, petroleum fluids, and motor oil. Use them to extend the life of your O-rings and improve their performance in high-pressure applications.

For technical drawings and 3-D models, click on a part number.

0.236" Wide
For Dash Number	ID	Thick.	Hardness	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
427	4.801"	0.117"	Durometer 90A (Hard)	-40° to 250°	Black	10	00000000	00000