AS568-117 Buna-N O-Rings: Sizing, Durometer and Fit

Quick answer

Choose an AS568-117 Buna-N o-ring when you need a 0.799 in. ID, 0.103 in. cross-section seal for air, water, or petroleum-based fluids between -40°F and +250°F and you want a firmer 90 durometer nitrile for static or high-pressure joints. Skip it for ketones, esters, strong acids, ozone, or continuous service above 250°F.

What dash 117 actually measures

AS568-117 is a standard dash number, not a brand-specific size. The 117 dash defines a 0.799 in. inside diameter with a 0.103 in. cross-section, so the outside diameter is roughly 1.005 in. before stretch or compression. That cross-section is thicker than the common 1/16 in. (0.070 in.) cord used in many small hydraulic and pneumatic ports, which changes both groove depth and squeeze.

If your groove was cut for a 0.070 in. cord, a 0.103 in. cross-section will not sit correctly. Check the groove width and depth against the AS568-117 dimensions before ordering, not just the inside diameter.

Why 90 durometer changes the fit decision

Durometer measures hardness on the Shore A scale. A 90 durometer o-ring is firmer than the common 70 durometer version of the same dash size. Firmer nitrile resists extrusion into gaps under pressure, which helps in static joints and higher-pressure assemblies. The trade-off is that 90 durometer seals need more compression force to seat and conform to imperfect surfaces.

For rough or pitted sealing faces, a softer 70 durometer o-ring often seals more reliably. For clean machined grooves under pressure, the 90 durometer AS568-117 is the more extrusion-resistant choice.

Temperature and chemical limits of Buna-N

Buna-N, also called NBR, nitrile, Chemigum, Hycar, or Perbunan, handles petroleum oils, greases, water, and air well within its rated range. The supplied service range for this AS568-117 is -40°F to +250°F (-40°C to +121°C). Continuous operation near the top of that range shortens seal life, so treat +250°F as a ceiling rather than a comfortable target.

Nitrile is not the right material for ketones, esters, strong acids, ozone, or prolonged sunlight. If your application involves those exposures, a different elastomer is the safer choice regardless of dash size.

Bulk quantity and cost per seal

This AS568-117 Buna-N o-ring is supplied in 800-piece packages. That volume suits maintenance shops, OEM assembly, and anyone replacing the same seal across multiple units. If you only need a handful for a one-off repair, the package size is the main drawback, not the seal itself.

Buying in bulk only pays off if the seals are stored correctly. Keep them away from ozone sources, direct sunlight, and heat, and rotate stock so older nitrile is used first.

Decision rules for AS568-117 o-rings

• Match the groove, not just the ID: Confirm your groove is cut for a 0.103 in. cross-section and 0.799 in. ID. If the groove was designed for a 0.070 in. cord, stop and select a different dash size. Measure groove width and depth before ordering.
• Choose 90 durometer for static and pressure: Use the 90 durometer AS568-117 for static seals, higher-pressure joints, and clean machined surfaces. Move to a softer durometer if the sealing face is rough or the assembly cannot tolerate stiff installation. Firmer nitrile resists extrusion but needs clean, well-machined surfaces.
• Check temperature before material: Stay within -40°F to +250°F and avoid continuous service at the top of that range. If the application runs hotter, or contacts ketones, esters, strong acids, or ozone, choose a different elastomer. Temperature and chemical exposure decide the material before dash size does.

Product facts

• 0.103" CS X 0.799" ID Buna-N Nitrile O-Rings | AS568-117 | Dash 117 | 90 Durometer (800 / Pkg.): AS568-117 Buna-N Nitrile o-rings with 0.799 in. ID, 0.103 in. cross-section, and 90 Shore A durometer, sold 800 per package. The firmer 90 durometer and thick cross-section suit static, higher-pressure joints, while the 800-piece pack fits repeat maintenance or production use.

  

Who should buy this o-ring

Best for

• Maintenance and repair teams replacing AS568-117 seals in air, water, or petroleum-fluid systems
• Static or higher-pressure joints that need a firmer 90 durometer nitrile seal
• Shops and OEMs that use the same dash size repeatedly and can use an 800-piece package

Not for

• Applications above +250°F or with ketones, esters, strong acids, or ozone exposure
• Grooves designed for a 0.070 in. cross-section cord
• One-off repairs where an 800-piece package is unnecessary