O-rings
X-rings (four-lobed rings)
An X-ring, also sold as a quad ring, is a four-lobed elastomer seal used in place of a round O-ring in reciprocating service, where its two sealing surfaces per side seal at less squeeze, run with less friction and resist the spiral twist that fails O-rings on long strokes. X-rings are sized on the same AS568 dash numbers as O-rings and are supplied in the same compound families.
- Section
- Four lobestwo sealing surfaces per side
- Sizing
- AS568 dashthe O-ring dash it replaces
- Cross-sections
- 5 cords0.070 to 0.275 in
- Service
- Reciprocatingrods, pistons, long strokes
What an X-ring is
An X-ring has a four-lobed cross-section instead of the round section of an O-ring. Each side of the ring presents two sealing surfaces, so it seals at less squeeze than a round section of the same size. The valleys between the lobes hold lubricant on a moving surface.
The mold parting line sits in the valley between two lobes, away from the sealing surfaces. On an O-ring the parting line lands on the sealing diameter itself, which is one reason the lobed section runs cleaner in dynamic service.
Quad-Ring® is the registered name of one manufacturer's four-lobed line. Generic X-rings from other molders cross to it in the same cross-sections when the print carries no brand or compound callout. Conquest Seal supplies X-rings from the molders it sources from and quotes the branded part when the print names it.
When an X-ring is chosen over an O-ring
The case for an X-ring is a reciprocating rod or piston, and it gets stronger as the stroke gets longer. Published gland guidance puts O-rings at their best on short strokes and small diameters, because a long stroke lets the ring roll and slide until it cuts itself in a spiral. The lobed section resists that roll.
In static service a round O-ring usually does the job and costs less to source. Send the current part number and Conquest Seal quotes the part it names, O-ring or X-ring.
| Feature | O-ring | X-ring |
|---|---|---|
| Sealing surfaces per side | 1 | 2 |
| Squeeze needed to seal | full squeeze on one round contact | less squeeze, two contacts |
| Mold parting line | on the sealing diameter | in the valley between lobes |
| Spiral twist, long-stroke reciprocating service | a known failure mode | resisted by the lobed section |
| Lubricant retention on a moving surface | none by design | held in the valleys |
| Size callout | AS568 dash | the same AS568 dash |
How X-rings are sized: AS568 dash numbers
An X-ring is specified by the AS568 dash number of the O-ring it replaces. The last three digits of an X-ring part number are that dash, with a manufacturer prefix in front of them: the four-lobed lines put the digit 4 in front of the dash, so 4214 is the -214 size on the 0.139 in cord; distributors often list the same part as Q4214. Quote the AS568 dash and the compound and the prefix follows.
The five cross-sections are the AS568 series. Each series links to the size chart, where every dash number has its own page with the inside diameter and tolerances the X-ring shares with the O-ring.
| Series | Dash range | W in | W mm | W tolerance in | Sizes |
|---|---|---|---|---|---|
| 0xx series | -004 to -050 (-001 to -003 run 0.040, 0.050 and 0.060 in) | 0.070 | 1.78 | +/- 0.003 | 47 |
| 1xx series | -102 to -178 | 0.103 | 2.62 | +/- 0.003 | 77 |
| 2xx series | -201 to -284 | 0.139 | 3.53 | +/- 0.004 | 84 |
| 3xx series | -309 to -395 | 0.210 | 5.33 | +/- 0.005 | 87 |
| 4xx series | -425 to -475 | 0.275 | 6.99 | +/- 0.006 | 51 |
The gland for an X-ring follows the X-ring manufacturer's design guide, which can call for a narrower groove than an O-ring of the same dash. Ask for the design sheet with the quote before cutting a new groove.
Compounds
X-rings are supplied in the same compound families as O-rings. The media and the temperature decide the family; the compound sheet sets the hardness and the limit for a specific grade.
| Family | ASTM D1418 | Standard range, C | Typical media |
|---|---|---|---|
| Viton® | FKM | -26 to 204 | fuels, oils, heat |
| Buna-N | NBR | -34 to 100 | mineral oils, hydraulic fluid |
| EPDM | EPDM | -57 to 150 | water, steam, glycol; never petroleum oils |
| Silicone | VMQ | -54 to 204 | dry heat and cold, static service |
| FFKM | FFKM | -26 to 320 | aggressive chemistry and temperature beyond FKM |
| HNBR | HNBR | -32 to 149 | oil with heat |
| Fluorosilicone | FVMQ | -73 to 177 | fuels at low temperature |
| Polyurethane | AU/EU | -40 to 82 | abrasion and high pressure |
| Aflas® | FEPM | -9 to 232 | steam, amines and sour gas; poor at low temperature |
| Butyl | IIR | -59 to 121 | gas impermeability, brake fluid and phosphate esters; never oil |
| Polyacrylate | ACM | -21 to 177 | hot transmission oil; poor at low temperature and in water |
| Ethylene-acrylic | AEM | -40 to 149 | hot automotive oil |
| SBR | SBR | no range on file | the compound sheet governs |
| Natural rubber | NR | no range on file | the compound sheet governs |
| Epichlorohydrin | ECO | no range on file | the compound sheet governs |
Related pages
Larger and non-standard sizes: an X-ring beyond the tooled sizes is supplied to order as a spliced and vulcanized O-ring on X-profile cord where that profile exists in the compound; send the diameter and the section.
Frequently asked
What is the difference between a quad ring and an O-ring?
A quad ring, or X-ring, has a four-lobed cross-section where an O-ring is round. The four lobes give two sealing surfaces per side, so the ring seals at less squeeze and with less friction, the mold parting line sits in a valley instead of on the sealing surface, and the lobed section resists the spiral twist that cuts O-rings on long reciprocating strokes. Both are sized on the same AS568 dash numbers.
Are X-rings and quad rings the same thing?
X-ring is the generic name for the four-lobed section. Quad-Ring is one manufacturer's registered name for its line of them. When a print names the brand and compound, quote that part; when it does not, a generic X-ring in the same cross-section crosses directly.
Can an X-ring replace an O-ring in the same groove?
The X-ring carries the same AS568 dash number and cross-section as the O-ring it replaces, so the size matches. The groove itself should be checked against the X-ring manufacturer's design guide, which can call for a narrower groove than the O-ring gland. Send the groove dimensions with the quote request and we send the X-ring maker's gland sheet with the quote.
How do I order an X-ring by size?
Send the AS568 dash number of the O-ring size, the compound and hardness, and the quantity. If you have a branded part number such as a 4214 or Q4214, send it as printed; the last three digits are the dash.
Which compounds are X-rings available in?
The same families as O-rings: nitrile for mineral oils and hydraulic fluid, EPDM for water and steam, FKM for fuels, oils and heat, silicone for dry heat and cold, and FFKM where the chemistry or the temperature exceeds FKM. The Parker O-Ring Handbook family ranges on file are listed above; the compound sheet governs a specific grade.
When is an O-ring the better choice?
In static service a round O-ring usually seals well and is easier to source in any size. The X-ring's advantages, less friction and resistance to spiral twist, only pay off on a moving rod or piston.
Related guides
Sources
AS568 cross-section series and dash ranges; Four-lobe section, parting line, lubricant valleys, 4-prefix numbering and the generic cross; Spiral failure on long strokes and large diameters (ERIKS); Parker O-Ring Handbook ORD 5700 compound family ranges. Dimensional facts are stated in our own words; no standard's text or table is reproduced.
Quad-Ring is a trademark of Trelleborg Sealing Solutions US, Inc.. No affiliation or endorsement is implied.
Viton is a trademark of The Chemours Company. No affiliation or endorsement is implied.
Aflas is a trademark of AGC. No affiliation or endorsement is implied.
Parker is a trademark of Parker Hannifin Corporation. No affiliation or endorsement is implied.
ERIKS is a trademark of its owner; no affiliation or endorsement is implied.
Send the dash number and the compound
The AS568 dash of the O-ring size, the compound and the quantity, or the branded X-ring part number as printed. A Conquest representative replies with the quote.
Request a quoteLast updated