O-Rings Technical Information

Basics of...O-Rings

O-rings are used for sealing in applications from high vacuum to high pressure
Used for sealing flanges, valves, faucets, compressors, engines, and boss tube fittings, O-rings are designated by an AS568A Dash Number
The AS568A Dash Numbers are assigned as an Aerospace Standard and are determined by the Society of Automotive Engineers
AS568A Dash Numbers are determined by the ID and OD of the O-ring
Metric O-rings are sized by measuring the cross-section, or width and the ID

The following chart will help determine the AS568A Dash Number and the O-ring material required for your application.

Size Guide

AS568A Dash No.	ID x OD	AS568A Dash No.	ID x OD	AS568A Dash No.	ID x OD	AS568A Dash No.	ID x OD	AS568A Dash No.	ID x OD
1/32 Cross Section		1/16 Cross Section		3/32 Cross Section		1/8 Cross Section		1/8 Cross Section
001	1/32 x 3/32	032	1 7/8 x 2	123	1 3/16 x 1 3/8	204	3/8 x 5/8	239	3 5/8 x 3 7/8
3/64 Cross Section		033	2 x 21/8	124	1 1/4 x 1 7/16	206	1/2 x 3/4	240	33/4 x 4
002	3/64 x 9/64	034	2 1/8 x 2 1/4	125	1 5/16 x 1 1/2	207	9/16 x 1 3/16	242	4 x 4 1/4
1/16 Cross Section		035	2 1/4 x 2 3/8	126	1 3/8 x 1 9/16	208	5/8 x 7/8	243	4 1/8 x 4 3/8
003	1/16 x 3/16	036	2 3/8 x 2 1/2	127	1 7/16 x 1 5/8	210	3/4 x 1	246	4 1/2 x 4 3/4
004	5/64 x 13/64	037	2 1/2 x 2 5/8	128	1 1/2 x 1 11/16	211	1 3/16 x 1 1/16	250	5 x 5 1/4
005	7/64 x 15/64	038	2 5/8 x 2 3/4	129	1 9/16 x 1 3/4	212	7/8 x 1 1/8	264	7 1/2 x 7 3/4
006	1/8 x 1/4	039	2 3/4 x 2 7/8	130	1 5/8 x 1 13/16	213	15/16 x 1 3/16	3/16 Cross Section
007	5/32 x 9/32	040	2 7/8 x 3	131	1 11/16 x 1 7/8	214	1 x 1 1/4	312	5/8 x 1
008	3/16 x 5/16	041	3 x 3 1/8	132	1 3/4 x 1 15/16	215	1 1/16 x 1 5/16	320	1 1/8 x 1 1/2
009	7/32 x 11/32	042	3 1/4 x 3 3/8	133	1 13/16 x 2	216	1 1/8 x 1 3/8	322	1 1/4 x 1 5/8
010	1/4 x 3/8	043	3 1/2 x 3 5/8	134	1 7/8 x 2 1/16	217	1 3/16 x 1 7/16	324	1 3/8 x 1 3/4
011	5/16 x 7/16	044	3 3/4 x 3 7/8	135	1 15/16 x 2 1/8	218	1 1/4 x 1 1/2	325	1 1/2 x 1 7/8
012	3/8 x 1/2	045	4 x 4 1/8	136	2 x 2 3/16	219	1 5/16 x 1 9/16	326	1 5/8 x 2
013	7/16 x 9/16	046	4 1/4 x 4 3/8	137	2 1/16 x 2 1/4	220	1 3/8 x 1 5/8	327	1 3/4 x 2 1/8
014	1/2 x 5/8	3/32 Cross Section		138	2 1/8 x 2 5/16	221	1 7/16 x 1 11/16	328	1 7/8 x 2 1/4
015	9/16 x 11/16	105	5/32 x 11/32	139	2 3/16 x 2 3/8	222	1 1/2 x 1 3/4	329	2 x 2 3/8
016	5/8 x 3/4	106	3/16 x 3/8	140	2 1/4 x 2 7/16	223	1 5/8 x 1 7/8	330	2 1/8 x 2 1/2
017	11/16 x 13/16	108	1/4 x 7/16	141	2 5/16 x 2 1/2	224	1 3/4 x 2	331	2 1/4 x 2 5/8
018	3/4 x 7/8	109	5/16 x 1/2	142	2 3/8 x 2 9/16	225	1 7/8 x 2 1/8	332	2 3/8 x 2 3/4
019	13/16 x 15/16	110	3/8 x 9/16	143	2 7/16 x 2 5/8	226	2 x 2 1/4	333	2 1/2 x 2 7/8
020	7/8 x 1	111	7/16 x 5/8	144	2 1/2 x 2 11/16	227	2 1/8 x 2 3/8	334	2 5/8 x 3
021	15/16 x 1 1/16	112	1/2 x 11/16	145	2 9/16 x 2 3/4	228	2 1/4 x 2 1/2	335	2 3/4 x 3 1/8
022	1 x 1 1/8	113	9/16 x 3/4	146	2 5/8 x 2 13/16	229	2 3/8 x 2 5/8	336	2 7/8 x 3 1/4
023	1 1/16 x 1 3/16	114	5/8 x 13/16	147	2 11/16 x 2 7/8	230	2 1/2 x 2 3/4	337	3 x 3 3/8
024	1 1/8 x 1 1/4	115	11/16 x 7/8	148	2 3/4 x 2 15/16	231	2 5/8 x 2 7/8	338	3 1/8 x 3 1/2
025	1 3/16 x 1 5/16	116	3/4 x 15/16	149	2 13/16 x 3	232	2 3/4 x 3	339	3 1/4 x 3 5/8
026	1 1/4 x 1 3/8	117	13/16 x 1	150	2 7/8 x 3 1/16	233	2 7/8 x 3 1/8	340	3 3/8 x 3 3/4
027	1 5/16 x 1 7/16	118	7/8 x 1 1/16	151	3 x 3 3/16	234	3 x 3 1/4	343	3 3/4 x 4 1/8
028	1 3/8 x 1 1/2	119	15/16 x 1 1/8	152	3 1/4 x 3 7/16	235	3 1/8 x 3 3/8	345	4 x 4 3/8
029	1 1/2 x 1 5/8	120	1 x 1 3/16	153	3 1/2 x 3 11/16	236	3 1/4 x 3 1/2	346	4 1/8 x 4 1/2
030	1 5/8 x 1 3/4	121	1 1/16 x 1 1/4	155	4 x 4 3/16	237	3 3/8 x 3 5/8
031	1 3/4 x 1 7/8	122	1 1/8 x 1 5/16	168	7 1/4 x 7 7/16	238	3 1/2 x 3 3/4

Application Guide

	Buna-N	Viton	Silicone	EPDM	PTEFE	Neoprene	Polyurethane	Kalrez®
Temperature Range	-65 to 275°F	-31 to 400°F	-65 to 450°F	-65 to 300°F	-300 to 500°F	-40 to 212°F	-60 to 200°F	0 to 500°F
Compression Set	GD	GD	GD	GD	PR	GD	GD	EX
Resistance to:
Tearing	GD	GD	PR	FR	GD	GD	EX	GD
Abrasion	EX	GD	PR	GD	PR	EX	EX	GD
Ozone	PR	EX	EX	EX	EX	EX	EX	EX
Weather	PR	EX	EX	EX	EX	EX	EX	EX
Cold Water	EX	FR	GD	EX	EX	FR	FR	GD
Hot Water	GD	PR	GD	EX	EX (To 212° F)	FR	PR	NR
Steam	PR	PR	PR	GD	EX	PR	PR	NR
Dilute Acid	GD	EX	GD	GD	EX	GD	PR	EX
Concentrated Acid	GD	EX	FR	GD	EX	GD	PR	EX
Dilute Alkalies	GD	EX	EX	EX	EX	GD	PR	EX
Concentrated Alkalies	GD	EX	EX	EX	EX	GD	PR	EX
Synthetic Lubricants (silicone grease)	GD	EX	NR	GD	EX	PR	PE	EX
High Aniline Lubricants (ASTM oil # 1)	EX	EX	GD	NR	EX	EX	GD	EX
Low Aniline Lubricants (ASTM oil # 3)	EX	EX	FR	NR	EX	GD	FR	EX
Vegetable/Animal Oil	GD	EX	EX	EX	EX	FR	EX	EX
Aliphatic Hydrocarbons (Fuel Oil A)	EX	EX	NR	NR	EX	FR	GD	EX
Aromatic Hydrocarbons (Fuel Oil C or Toluene)	PR	EX	NR	NR	EX	PR	FR	EX

NR= Not Recommended;
PR= Poor;
Fr= Fair;
GD= Good;
EX= Excellent

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