Materials -- O-rings can be made of a very long list of exotic materials; most are inappropriate for SCUBA applications. The materials commonly used in SCUBA applications appear in the following table.

Hardness -- 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 O-rings sold on this page are 90-duro (except for the -003 SPG O-ring), and well suited for the SCUBA applications we describe. 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.

Color -- O-rings are available in nearly any color, although most commonly seen in black. Most Viton O-rings are black. The Viton O-rings sold on this page 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 COLOR of the O-ring is MEANINGLESS. Some people believe there is a difference in quality based on color, 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 color alone, and independent testing supports that statement. Some people also incorrectly believe a 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 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.

OEM-Supplied O-Rings -- Designers of modern SCUBA equipment often specify O-rings with special properties and materials for specific uses inside their equipment, particularly regulator internal o-rings. The special o-rings are supplied as part of factory service parts kits. Substituting any other generic O-ring just because it's the right size can cause difficult-to-diagnose problems and degrade performance. Many of the high piece count generic o-ring kits for scuba contain a lot of o-rings that are sizes only used inside regulators. However, most modern quality regulators now use specialized o-rings thus making many of the o-rings in large kits useless and a very poor value.

Beware of Imitation Oxygen Compatible O-rings

Viton is DuPont Performance Elastomer's brand name for fluorocarbon based elastomers (FKM). The Viton O-rings sold at Dive Gear Express are 100% virgin Viton family type "A.". Products not made from Viton may fall short of the expected performance. However, DuPont Performance Elastomers is not the only company that manufactures FKM products. Bear in mind that not all FKMs are equivalent, and there are even different types of Viton O-rings intended for various different applications. Many people incorrectly refer to any and all FKM O-rings or even generic "oxygen-compatible" O-rings as Viton. Like "Rolexx" wristwatches, the industry has begun to see a lot of imitation Viton, particularly with O-rings manufactured outside the US. As a result, you could end up with O-rings that are not the type of Viton you need, and most likely not even an oxygen compatible O-ring at all. Note the color of the O-ring is meaningless, we've seen impostor Viton O-rings that were actually a mixture of a little Viton and mostly cheap plain rubber, yet were also brown. The problem has become so widespread that we've had to resort to certification testing to verify our O-rings are as described and now make up our own kits. We're going to be very frank: the 'asian import' o-ring kits in the little plastic compartmentalized boxes are not 'as advertised', we know because we had them tested.

Beware of Repackaged Lubricant: Some other vendors are purchasing oxygen compatible lubricants in bulk containers and then repackaging it in smaller 1/4-oz or 1/2-oz sizes. Aerospace Lubricants has advised us this is an unapproved and possibly unsafe practice. These unapproved package types contain mold release agents, silcone treated rubber stoppers in the syringes, and dyes in colored containers, all of which can leach into the lubricant itself. These containers, along with the repackaging conditions themselves, are certain to produce lubricants which are contaminated and no longer suitable for oxygen service. Dive Gear Express only sells lubricants that are supplied directly from the factory in their carefully selected packaging.

How Much and Where to Use Lubricant

Some people very sparingly lubricate the SPG swivel O-rings, but you should know that SPG and hose assemblies from our suppliers are never lubricated. If you do choose lube the SPG swivel o-rings, take care not to be so generous that lube might migrate up into the Bourdon tube mechanism and cause your SPG to become inaccurate. Some people also sparingly lubricate the threads of valves before they are installed in the cylinder neck. Do NOT lubricate the neck O-ring itself, and absolutely positively do not lubricate the valve/regulator seal O-ring or DIN threads. Most lubricant is used with dynamic seals in regulators and other equipment with moving parts. As a general rule, the O-rings used with static seals in SCUBA applications should not be lubricated at all. The lubricant just causes contamination to stick to the surface of the O-ring and results in more problems with a static seal than any dubious benefit the lubricant might provide.

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