Dash Number 351 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"

4.778"

	OD OD

5.145"

	Dash Number Dash Number	Show

351

	Dash Number Dash Number	Hide

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	Width Width

0.183"

0.210"

	Fractional Width Fractional Width

3/16

	Hardness Hardness

	Hardness Rating Hardness Rating


Soft	Medium

Hard

	Material Material

Plastic

Rubber

	Color Color

	Black		Red
	Brown		Clear

	Fractional ID Fractional ID

4 3/4

	For Use With For Use With

	Specifications Met Specifications Met

	Fractional OD Fractional OD

5 1/8

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

DFARS Specialty Metals
COTS-Exempt

	Maximum Temperature Maximum Temperature

Less than 250° F

250° to 299° F

400° to 499° F

	Minimum Temperature Minimum Temperature

-99° to -50° F

-49° to 0° F

	RoHS (Restriction of Hazardous Substances) RoHS (Restriction of Hazardous Substances)

RoHS Compliant

	REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) REACH (Registration, Evaluation, Authorization and Restriction of Chemicals)

REACH Compliant

	Construction Construction

Solid

	Thickness Thickness

0.076"

	Core Material Core Material

Viton® Fluoroelastomer
Rubber

Silicone Rubber

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14 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.: 3/16 Fractional (0.210" Actual)
351	4 3/4	5 1/8	4.725"	5.145"	Durometer 70A (Medium)	ASTM D2000, SAE AS568, SAE J200	-20° to 250°	Black	5	00000000	00000

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.: 3/16 Fractional (0.210" Actual)
351	4 3/4	5 1/8	4.725"	5.145"	Durometer 70A (Medium)	ASTM D2000, SAE AS568, SAE J200	-30° to 212°	Black	10	00000000	000000

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.: 3/16 Fractional (0.210" Actual)
351	4 3/4	5 1/8	4.725"	5.145"	Durometer 70A (Medium)	ASTM D2000, SAE AS568, SAE J200	-30° to 225°	Black	5	000000000	00000

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.: 3/16 Fractional (0.210" Actual)
351	4 3/4	5 1/8	4.725"	5.145"	Durometer 65A (Medium)	ASTM D2000, MIL-I-45208, SAE AS3578, SAE AS568, SAE J200	-20° to 250°	Black	1	00000000	00000

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.: 3/16 Fractional (0.210"Actual)
351	4 3/4	5 1/8	4.725"	5.145"	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.: 3/16 Fractional (0.210" Actual)
351	4 3/4	5 1/8	4.725"	5.145"	Durometer 75A (Medium)	ASTM D2000, SAE AS568, SAE J200	0° to 400°	Black	2	00000000	00000

Chemical-Resistant Hard Viton® Fluoroelastomer O-Rings

These hard O-rings offer better wear resistance than standard Viton® fluoroelastomer O-rings. They resist a wide range of chemicals, including benzene, butyl alcohol, and ethylene glycol. All have a round profile and are suitable for both 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	Hardness	Specifications Met	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
Wd.: 3/16 Fractional (0.210" Actual)
351	4 3/4	5 1/8	4.725"	5.145"	Durometer 90A (Hard)	ASTM D2000, SAE AS568, SAE J200	-20° to 400°	Black	2	00000000	000000

Chemical-Resistant Brown Viton® Fluoroelastomer O-Rings

Because one black O-ring looks just like another, these Viton® fluoroelastomer O-rings are brown for easy identification. They resist a wide range of chemicals, including benzene, butyl alcohol, and ethylene glycol. All have a round profile and are suitable for both static and dynamic sealing applications. O-rings have shelf life, cure date, and traceable lot number printed on the bag.

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.: 3/16 Fractional (0.210" Actual)
351	4 3/4	5 1/8	4.725"	5.145"	Durometer 75A (Medium)	ASTM D2000, SAE AS568, SAE J200	-15° to 400°	Brown	2	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.:3/16 Fractional (0.210" Actual)
351	4 3/4	5 1/8	4.725"	5.145"	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.:3/16 Fractional (0.210" Actual)
351	4 3/4	5 1/8	4.725"	5.145"	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.: 3/16 Fractional (0.210" Actual)
351	4 3/4	5 1/8	4.725"	5.145"	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.: 3/16 Fractional (0.210" Actual)
351	4 3/4	5 1/8	4.725"	5.145"	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.: 3/16 Fractional (0.210" Actual)
351	4 3/4	5 1/8	4.725"	5.145"	Durometer 70A (Medium)	ASTM D2000, SAE AS568, SAE J200	-70° to 250°	Black	10	00000000	000000

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.

0.183" Wide
For Dash Number	ID	Thick.	Hardness	Temperature Range, °F	Color	Pkg. Qty.		Pkg.
351	4.778"	0.076"	Durometer 90A (Hard)	-40° to 250°	Black	10	0000000	00000