AS568-350

Standard Imperial O-Ring Size

Dimensions

Inside Diameter (inch)	4.600 in
Cross Section (inch)	0.210 in
Inside Diameter (mm)	116.84 mm
Cross Section (mm)	5.33 mm
Recommended Groove Depth	0.172 in
Theoretical Static Compression	18.3% (Target: 15-25%)

Quick Reference

ID: 4.600" (116.84 mm)

CS: 0.210" (5.33 mm)

Static Compression: 18.3%

Target Range: 15–25% static, 10–20% dynamic

Groove Depth: 0.172 in

Groove Width: 0.252 in (1.2× CS)

About This Size

AS568-350 is a AS568 300 Series imperial O-ring with 4.600" inside diameter (116.84 mm) and 0.210" cross section (5.33 mm). At the recommended groove depth of 0.172", theoretical static compression is 18.3% — within the typical 15–25% target for static glands. This dash number is widely stocked in NBR, FKM, EPDM, VMQ, and PTFE for large flanges, heavy hydraulics, process equipment.

Part of AS568 300 Series

Adjacent Sizes

AS568-349

Smaller ID (same cross section)

AS568-351

Larger ID (same cross section)

Cross-Standard Reference

Standard	Nearest Size	ID Δ	CS Δ
ISO 3601	118.00x3.55	1.16 mm	1.78 mm
JIS B 2401	P-5.70x118.00	1.16 mm	0.37 mm

Cross-reference values are catalog nearest matches — always verify groove width, depth, and tolerance class on your drawing before substituting standards.

Compression Rate Guidance

Static seals: 15–25% compression is ideal for most fixed applications.
Dynamic seals: 10–20% compression to reduce friction and wear.
Groove width should typically be 1.1 to 1.3 times the O-ring cross section.
Surface finish: Ra 0.8–3.2 µm for static, Ra 0.4–0.8 µm for reciprocating dynamic service.

Typical Applications

Large hydraulic assemblies
Supports heavy-duty cylinder heads, press platens, and mobile equipment covers at 117 mm nominal ID.
Pipeline & tank closures
Used on manway covers, valve bonnets, and static flange joints where groove width allows a robust cross section.
High-load static joints
The larger cross section tolerates wider extrusion gaps and higher bolt loads on flat-face flanges.

Tolerance & Standard Notes

AS568 defines a single tolerance table that applies to every dash number (the two-class system of the 1971 issue was merged in AS568A). For critical dynamic seals, tighter-than-standard dimensional tolerances agreed with the manufacturer (per drawing) are the standard route; surface quality is specified separately under ISO 3601-3 grades N, S, or CS.

For tolerance details, see the O-Ring Tolerance Guide.

Design FAQ

What AS568 series is dash 350?

AS568 300 Series covers dash 350 with a 0.210" (5.33 mm) cross section. Large flanges, heavy hydraulics, process equipment

What extrusion gap is safe for this size?

For a 0.210" cross section, limit the diametral extrusion gap to 0.004–0.006" (0.10–0.15 mm) for pressures up to 150 bar. Above 150 bar, use a PTFE backup ring regardless of gap size.

What hardness should I specify?

70 Shore A is the standard for most static and dynamic applications up to 100 bar. Use 80 Shore A for 100–200 bar dynamic service. Use 90 Shore A only for extreme extrusion resistance or abrasive conditions.

What is the nearest ISO 3601 metric equivalent to AS568-350?

The closest ISO 3601 catalog size is 118.00x3.55 (ID 118.00 mm × CS 3.55 mm). ID differs by 1.16 mm — verify groove dimensions before substituting.

When do I need a backup ring?

Use a backup ring when pressure exceeds 1,500 psi (100 bar) or when the extrusion gap is larger than 0.15 mm for this cross section. PTFE backup rings are standard for AS568 sizes.

Related Resources

Imperial Size Chart

Browse the full AS568 table when you need adjacent dash numbers or series comparisons.

View AS568 chart

Size Converter

Convert this imperial size to metric equivalents before choosing ISO or JIS alternatives.

Open size converter

Compression Calculator

Check gland squeeze and confirm whether your groove depth matches the target compression range.

Calculate compression

AS568 PDF Download

Request the printable size chart for engineering review, quoting, or shop-floor reference.

Request AS568 PDF