Jul. 28, 2025
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If you're buying O-rings online, you sometimes know the exact part number and quantity you need. At other times, you may just know certain attributes of the O-ring you need. For example, the dimensions must be 1.78 x 1.02 mm, or it should be made of silicone.
With competitive price and timely delivery, htob sincerely hope to be your supplier and partner.
Or it could be that you need an O-ring suitable for use with drinking water processes or one that can tolerate contact with petroleum products.
At Freudenberg Sealing Technologies, we have an easy process for finding O-rings and ordering them online. Here's how you can find the right O-ring on our website and place your order with ease.
Finding the right O-ring
To buy O-rings online, you need a trade account, which you can apply for through our Trade Account Access page.
To find your O-ring, select from the ‘O-ring Kits’ dropdown menu found on each web page, or choose the ‘Seal Products’ dropdown menu and look in the O-ring category. O-rings are listed by material type, e.g. EPDM, silicone, nitrile.
Once you’ve found the O-ring, click on it, choose the quantity and proceed to the checkout.
If you’re not sure about the materials, but have the dimensions of the seal you need, you can use the Seal Filter & Finder on the top right of the page. Once you have entered the dimensions, any matching products are displayed and you can make your choice.
Detailed O-ring information
If you need to know more about any O-ring, the Freudenberg E-Catalogue describes each one in great detail. The catalogue is searchable by O-ring type, dimensions, materials and/or Shore hardness.
Each O-ring has a material data sheet showing its physical properties (density, hardness, modulus) and its conformity to standards such as DIN, EC, AS/NZS, NSF and FDA. The data sheet also indicates the application for which the O-ring is suitable – food production, fuel lines or hydraulics, for example.
Buying O-rings online is a convenient way of ensuring you always have replacement parts in stock. Because whether you’re maintaining a utility-scale asset or repairing a washing machine motor, a missing O-ring costing just a few cents can hold up an entire operation.
Many items of scuba diving equipment contain rubber O-rings that perish, dry out and develop cracks as time goes by. Even if the dive gear is not used, once it is a few years old, all the O-rings will need replacing.
An O-ring is a doughnut, or torus shaped seal typically used to prevent the passing of air or fluid. In other words, O-rings are used to keep fluid or air IN or OUT of a defined space. For example, an underwater camera housing uses O-rings to keep water out, and scuba regulators use O-rings to prevent precious air from escaping.
Just as barbed wire and duck tape seems to fix everything on land, O-rings and tie wraps seem to fix anything when you're at sea. These tiny rubber rings are crucial parts of a variety of scuba diving gear and equipment. O-rings prevent leaks at the seams of scuba gear and are a vital part of your life support equipment while diving. O-rings are used in scuba regulators, underwater lights and strobes, dive computers and cylinder/tank valves, and may often break due to pressure and wear and tear.
If you work on dive gear you know the importance of having the correct O-rings. Many of the O-rings used on cylinders, valves and regulator hoses are pretty much generic. Having a large selection of common O-rings is a must for the serious technical diver.
However, if you aren't well versed in the technical aspect of scuba gear, it's only advisable to attempt to change the O-ring on a scuba cylinder/tank valve (Yoke), or the face of your DIN regulator. Leave other O-rings for experienced professionals.
The information that follows should help you to know more about the O-rings used in various scuba diving applications.
In the USA the Society of Automotive Engineers (S.A.E.) publishes AS568B as an Aerospace Standard that specifies sizes for O-rings used in sealing applications. The equivalent British Standards Institution publication is BS, which lists all Imperial standard sizes. This standard includes all of the 5 main cross section groups in AS568, plus several sizes that are "between" AS568 sizes. In Australia BS is widely referenced in many industries, including the dive industry.
The BS number is a three-digit suffix that identifies the O-ring's size. Technically, an O-ring size is listed as BS-016, BS-112, etc., but most people use BS and the three-digit number (e.g. BS112), or just the three-digit number (e.g. 112). The first digit denotes the O-ring cross section width: 0xx = 1/16-inch, 1xx = 3/32-inch, 2xx = 1/8-inch.
While it might seem convenient to provide a picture sizing chart, we've never seen an online version that could be reproduced exactly in a Web browser. However, you can download and print our Scuba O-Ring Sizes Chart (Adobe PDF | 356.37 KB) — Chart showing scuba diving O-ring sizes.
Please remember that sizing an existing O-ring that has been in service can be error prone because O-rings can take a set that changes their dimensions enough to be misleading. Luckily, the sizes used in 'user serviceable' SCUBA applications are fairly regular, so it's probably best to choose the size based upon the application.
BS- OD ID CS SCUBA Application Seal 214 1-1/4" 1"O-rings can be made of a very long list of exotic materials and most are inappropriate for SCUBA applications. The materials commonly used in SCUBA applications appear in the following table.
Material Description Acrylonitrile-Butadine Copolymers
The Difference between FPM, FKM and Viton®
The terms FPM, FKM and Viton® very often cause confusion and lead to incorrect interpretations. All of these designations actually stand for one single base material: fluoro rubber.
O-rings are normally available with a hardness rating, as measured by an ASTM type-A durometer, of 70 (the "soft" kind) or more rarely a rating of 90 (the "stiff" kind). The soft O-rings are appropriate for dynamic applications where the O-ring is providing a seal with a constantly moving part, such as inside regulators. The stiff O-rings are more durable in static applications where the O-ring is providing a seal with stationary or occasionally moving parts, such as a valve.
O-rings are available in nearly any colour, although most commonly seen in black. Most FPM/FKM/Viton® O-rings are black. The FPM/FKM/Viton® O-rings typically sold for scuba diving are brown, simply to make them easily distinguishable from Nitrile O-rings which are usually black and EPDM O-rings which are often purple. Just to be clear, the COLOUR of the O-ring is MEANINGLESS.
The company is the world’s best O-Ring Sets supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.
Related links:Some people believe there is a difference in quality based on colour, but that is more likely attributed to unknowingly using soft dynamic O-rings in static applications. Our O-ring manufacturer states there is little difference in quality for O-rings based on colour alone, and independent testing supports that statement.
Some people also incorrectly believe a FPM/FKM/Viton® O-ring can be distinguished from a Nitrile O-ring by the surface appearance. Nitrile O-rings are said to have a shiny surface, and FPM/FKM/Viton® O-rings are said to have a matte surface. This is not a reliable indicator, and certainly not true if the O-ring has been lubricated.
Remove the old O-ring visible in the orifice of the tank's regulator valve. For this you should use a brass O-ring pick which looks similar to that of a dental pick (pictured right). This is because metal tweezers or other objects can damage the o-ring groove, and even the slightest dent of the groove can cause leaks. A plastic toothpick too is a safe tool to use if you don't have an O-ring pick.
Using the pick, scoop the old O-ring out and clean out the groove using the same plastic toothpick or professional pick. Look out for sand or debris and keep an eye out for any corrosion. If you spot any, you may want to have a professional take a look at it.
Check your replacement O-ring against the one you removed. Confirm they are of similar size and materials.
Push the new O-ring into the groove to replace the old one. It should slip in easily. If you have to stretch or force it, it's probably not the right size. Never use silicone grease. This is especially to be avoided if you are using a nitrox mix (a combination of nitrogen and oxygen). Silicone reacts with oxygen. Avoid using anything other than your finger or the back eraser end of a pencil to seat the O-ring.
Make sure the new o-ring you just put in doesn't have any nicks, cuts or stretch marks on it. If it does, replace it with a new one again.
Test the new O-ring, by attaching the first stage of your regulator like you would normally do. Slowly open the cylinder valve to pressurize the regulator. If you hear a loud pop or clap and air hissing out, the O-ring is not properly seated. Go back to the beginning and try again.
Trident Brass O-Ring 3 Piece Tool Set
RRP: $29, Our Price: $25, You Save $4 (14%).
This tool set combines three brass picks for the removal of O-rings from regulators, scuba tanks valves and so on.
Apeks Regulator Travel Kit
This table lists the O-Rings used for servicing Apeks regulators for the following models:
* First stages: US4, DS4, UST, DST, FST(ATX100), FSR(ATX200)
* Second stages: T20, TX40/50/100/200, AT20, ATX40/50/100/200
Please download/view the Apeks Spare Parts and O-Ring Identification Chart (Adobe PDF | 308.83 KB).
Please download/view the Scubapro O-Rings Chart (Adobe PDF | 59.32 KB).
The ISO standard specification for dimensions of the O-ring groove in the nose of the 232 bar and 300 bar DIN connectors for compressed air has an inside dimension of 12 mm and an outside dimension of 17 mm. In , the standard depth for the groove was revised from the original 1.9 mm to a slightly deeper 2 mm. The specification for the sealing O-ring itself is an inside diameter of 11.2 mm with a cross section of 2.65 mm. From what we have been able to determine, not all SCUBA regulator manufacturers seem to use the current standard groove and O-ring in the universal DIN fittings found on their first stages.
The sealing O-ring in the nose of the DIN connector groove we find on most SCUBA regulator first stages is commonly an SAE AS568 and BS ISO imperial standard 112 size that is equivalent to 12.37 X 2.62 metric dimensions. In the case of a few regulators (notably Apeks, Atomic, and ScubaPro brands) their groove better accepts the next smaller 111 size O-ring that is equivalent to 10.77 X 2.62 metric dimensions. Both the 112 and 111 size O-rings are very common sizes available in a variety of choices for material and durometer.
The groove in the Cressi and Poseidon brand regulator DIN connectors measures closest to the original standard, best accepting a BS ISO metric size O-ring with 11.3 X 2.4 dimensions for which there is no imperial standard equivalent. The M2.4X11.3 size O-ring is uncommon, especially in a material suitable for use with Nitrox. (FYI, the O-ring in Yoke K-valves is easy, it is always an 014 size.)
Compared to the 111 size, the M2.4X11.3 size is slightly smaller cross section and slightly larger diameter with a good fit for the O-ring groove of the DIN connectors on Cressi and Poseidon regulators. Because of availability, most Nitrox and technical divers make do with a 111 size O-ring for their Cressi and Poseidon regulators, but the 111 is not as good a fit for the connector of those two brands.
In the European Union nations, the EN 144-3: standard requires a valve outlet known as M26x2 to be used on dive cylinders containing oxygen or Nitrox mixtures with greater than 22% oxygen. The M26x2 outlet is similar in appearance but slightly larger than the standard DIN outlet, and thus incompatible with the standard DIN connector found on SCUBA regulators. The purpose of this incompatible valve outlet is to force the dedication of cylinders, regulators and fill stations to Nitrox use. The sealing O-ring in the nose of the M26x2 connector is 13.9 X 2.6 metric dimensions, equivalent to the 113 size. The M26x2 outlet and connector for Nitrox and oxygen is very rarely seen outside the EU.
At The Scuba Doctor Dive Shop we keep the following O-rings commonly used on the face of DIN regulators and cylinder/tank valves in stock for purchase in-store as emergency replacements:
Sonar DIN O-Rings for Cressi and Poseidon First Stages (10 Pack)
RRP: $12, Our Price: $9, You Save $3 (25%).
The Sonar DIN O-Rings for Cressi and Poseidon First Stage Regulators are a great save a dive kit item. The O-rings in this pack of 10 are coloured Yellow which makes it easy to identify them.
Sonar DIN O-Rings for Apeks and Scubapro First Stages (10 Pack)
RRP: $12, Our Price: $9, You Save $3 (25%).
The Sonar DIN O-Rings for Apeks and Scubapro First Stage Regulators are a great save a dive kit item. The O-rings in this pack of 10 are coloured Red which makes it easy to identify them.
Sonar DIN O-Rings for Mares First Stages (10 Pack)
RRP: $12, Our Price: $9, You Save $3 (25%).
The Sonar DIN O-Rings for Mares First Stage Regulators are a great save a dive kit item. The O-rings in this pack of 10 are coloured Blue which makes it easy to identify them.
Sonar Scuba O-Ring - 112 NBR 90 Duro - Black (10 Pack)
RRP: $10, Our Price: $8, You Save $2 (20%).
This is the O-ring size typically used at the front and back of the DIN insert used to convert standard DIN valves to INT/Yoke valves. These are the O-rings we prefer to use on the Faber / San-o-Sub DIN/K valves on Faber steel cylinders. We prefer these harder 90 durometer O-rings over the softer 70 duro ones commonly used.
Sonar Scuba O-Ring - 112 Viton/FPM 75 Duro - Brown (5 Pack)
RRP: $15, Our Price: $11.50, You Save $3.50 (23%).
This is the O-ring size typically used at the front and back of the DIN insert used to convert standard DIN valves to INT/Yoke valves. These are the O-rings we prefer to use on the Faber / San-o-Sub DIN/K valves on Faber steel cylinders that are being used for Nitrox or Oxygen.
Trident O-Ring Kit and Pick
RRP: $29, Our Price: $26, You Save $3 (10%).
A mini scuba cylinder/tank container with Brass Pick and 10 popular diver O-Rings. A must for any diver's spares kit!
We have a range of O-Rings and Lubricants available for purchase from our online dive shop.
For more information, please visit EC Cup End VK Oil Seal.
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