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ORING

Description & Features

Manufactured by Hercules Sealing Products, this standard-profile O-ring measures 5.48 inches inner diameter and 5.90 inches outer diameter, with a cross-section width of 0.21 inches. Nominal dimensions are listed as 5-1/2 inch ID, 5-7/8 inch OD, and 3/16 inch width, making it straightforward to match against existing seal specifications or replacement requirements.

This O-ring is suited for static and dynamic sealing applications in hydraulic and industrial equipment where consistent, reliable performance at this size range is required. The dimensional profile is consistent with common industry sizing conventions, supporting use as a direct replacement in a range of hydraulic cylinders, valves, and fluid power assemblies.

SKU: 568-357

Supplier Part Number (MPN): 568-357

Alternate Part Numbers: A-357, C1CF99, MI-08740555, MINO-00407X21602

Specifications

Actual I.D. 5.48 Inch	Actual O.D. 5.90 Inch	Actual Width 0.21 Inch	Alternate Part Numbers Alternate Part Number A-357, Alternate Part Number C1CF99, Alternate Part Number MI-08740555, Alternate Part Number MINO-00407X21602	Brand Hercules Sealing Products	Brand Hercules Sealing Products	Pack Size 1.00	UOM EA	Nominal I.D. (in) 5-1/2	Nominal O.D. 5-7/8	Nominal Width 3/16	Supplier Part Number 568-357	Product Weight 0.03 lbs

Product Questions & Answers (3)

Question by: Hubert H on Feb 28, 2026, 9:33 AM

trying to swap out an old seal, are these numbers the real size or just “nominal”?

Answer by: Customer Support on Mar 2, 2026, 7:22 AM

Go by the actual dimensions: 5.48 inch inner diameter, 5.90 inch outer diameter, and 0.21 inch cross-section width. The nominal callouts (5-1/2 inch ID, 5-7/8 inch OD, 3/16 inch width) are the rounded sizing used for matching common industry seal sizes.

Question by: Johnny M on Oct 23, 2025, 10:20 AM

Got an old cylinder seal that needs replacing, part number on it reads A-357. That the same as this one?

Answer by: Customer Support on Oct 24, 2025, 8:31 PM

A-357 is one of the alternate part numbers tied to this exact o-ring, so you're looking at a direct match. The SKU here is 568-357, made by Hercules Sealing Products. Same seal, just cross-referenced under a different number. You should be good to go.

Question by: Jerry G on Jul 17, 2025, 4:00 PM

Is this oring generally good for hydraulics, like for cylinders and stuff?

Answer by: Customer Support on Jul 18, 2025, 5:53 PM

It is indeed suitable for both static and dynamic sealing tasks within hydraulic systems. This O-ring is designed for use in hydraulic cylinders, valves, and other fluid power assemblies.