8-368 BLACK BUNA 90D BACK-UP RING

Buna-N Back-Up Ring, 7.725 in ID x 0.21 CS, 90A, Black, -40 to 250°F

Status
Available
Est. Ship Date
31 Oct 2026
Material
Buna-N (Nitrile / NBR)
Dash Size
368
Durometer
90 Shore A
Cross Section Type
Round
Color
Black
Minimum Temperature
-40°F (-40°C)
Maximum Temperature
250°F (121°C)
Nominal Cross Section
3/16 inch
Nominal Inside Diameter
7 3/4 inch
Nominal Outside Diameter
8 1/8 inch
Unit of Measure
EA
SKU:
HB90368
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Product Specification

-
APG stocks the HB90368, an AS568-368 black Buna-N (Nitrile) 90 Shore A Back-Up Ring with an inside diameter of 7.725 in (196.22 mm), a cross section of 0.21 in (5.33 mm), and an outside diameter of 8.145 in (206.88 mm). A back-up ring installs on the low-pressure side of an o-ring to prevent extrusion into the clearance gap at elevated pressure.

Buna-N (Nitrile) is specified here for economical choice for high-volume maintenance programs, reliable performance in both static and dynamic service. Expect good resistance to many alcohols, petroleum-based oils, and propane and butane. Rated temperature range runs from -40°F (-40°C) to 250°F (121.1°C) in continuous service. Applications involving strong acids or ketones call for a different compound.

Typical settings include hydraulic and pneumatic systems, construction equipment, and fluid power.

HB90368 ships individually. Unit weight is approximately 6.588 g. Review your operating media and conditions against this specification before installation.
Item
HB90368
Description
8-368 BLACK BUNA 90D BACK-UP RING
Actual Cross Section
0.21 inch (5.33 mm)
Actual Inside Diameter
7.725 inch (196.22 mm)
Actual Outside Diameter
8.145 inch (206.88 mm)
FDA Compliant
No
Measurement System
Imperial
Metal Detectable
No
NSF Certified
No
Product Code
6002
Product Category
O-Rings - Backup Rings