O-Ring NBR 18x4 mm 70 ShA

O-Ring NBR 18x4 mm 70 ShA (1000 pcs)

O-Ring NBR 18x4 mm 70 ShA is an elastomeric sealing ring with a nominal inside diameter (ID) of 18 mm and cross-section (CS) of 4 mm. It is manufactured from NBR - Nitrile Butadiene Rubber with a nominal hardness of 70 Shore A. The exact simmering.pl product is identified as GRN®, reference 18X4*, and this commercial variant contains 1000 pcs.

Complete technical identification:

GRN® + O-Ring + 18x4 mm + NBR + 70 Shore A + 1000 pcs

O-Ring NBR 18x4 mm 70 ShA - Technical Characteristics

The principal identification parameters are:

Brand: GRN®

Product type: O-Ring / elastomeric sealing ring

Reference: 18X4*

Nominal size: 18x4 mm

ID - Inside Diameter: 18 mm

CS - Cross-Section: 4 mm

Calculated OD - Outside Diameter: 26 mm

Material: NBR

Material name: Nitrile Butadiene Rubber

Nominal hardness: 70 Shore A

Alternative hardness notation: 70 ShA

Cross-section: Circular

Package quantity: 1000 pcs

The exact simmering.pl product data confirm 18 mm inside diameter, 4 mm cross-section, NBR, 70 Shore A and GRN®. The product page also identifies the 1000-piece bulk variant.

Independent technical catalogues also list the exact dimensional/material combination 18x4 NBR 70 Shore A.

O-Ring 18x4 mm Dimensions

The standard dimensional designation is:

18x4 mm

where:

ID = 18 mm - nominal inside diameter

CS = 4 mm - nominal cross-section diameter

The outside diameter can be calculated geometrically:

OD = ID + 2 x CS

Therefore:

OD = 18 + (2 x 4)

OD = 26 mm

The dimensional relationship is:

ID = 18 mm

CS = 4 mm

Calculated OD = 26 mm

The primary catalogue size remains:

18x4 mm

The calculated outside diameter should not replace the standard ID x CS product identification.

O-Ring Construction

An O-ring is a closed elastomeric sealing element with a circular cross-section.

Its sealing function is created by controlled deformation of the elastomer after installation in an appropriately designed groove.

When the mating components are assembled, the O-ring cross-section is compressed between the sealing surfaces. This produces the contact required for sealing.

Unlike a radial shaft seal, a conventional O-ring does not incorporate a sealing lip, garter spring or metal reinforcing ring.

The complete sealing arrangement therefore consists of the O-ring, groove geometry and mating surfaces.

NBR - Nitrile Butadiene Rubber

The confirmed material is:

NBR - Nitrile Butadiene Rubber

The exact material designation forms an integral part of the product identification:

O-Ring NBR 18x4 mm

The exact GRN® product page identifies the material as NBR, while independent suppliers also catalogue the 18x4 mm size in NBR 70 Shore A.

An O-ring with identical dimensions manufactured from FKM, EPDM, VMQ or another elastomer should not automatically be considered the same technical variant.

The elastomer must therefore be considered together with dimensions and hardness when selecting a replacement.

70 ShA / 70 Shore A Hardness

The confirmed nominal hardness is:

70 Shore A

also written as:

70 ShA

The exact simmering.pl product page specifies 70 Shore A, and independent 18x4 mm products from Athena and HANSA-FLEX confirm the established 18x4 NBR 70 Shore A specification.

Hardness is an integral part of the technical identification:

18x4 mm + NBR + 70 Shore A

A dimensionally identical:

18x4 mm NBR 80 Shore A

or:

18x4 mm NBR 90 Shore A

should not automatically be treated as the same technical variant.

How Does an O-Ring Work?

An O-ring is installed in a groove designed for the required sealing arrangement.

After assembly, its circular cross-section is compressed between the mating surfaces. This controlled deformation generates sealing contact.

The behaviour of the complete sealing system depends on factors including:

O-ring dimensions

groove geometry

compression

stretch

elastomer material

hardness

operating medium

temperature

pressure

static or dynamic operating conditions

Correct selection therefore requires more than simply matching the nominal 18x4 mm dimensions.

What Does 18x4 NBR 70 ShA Mean?

The designation can be interpreted as:

18 mm - nominal inside diameter (ID)

4 mm - nominal cross-section (CS)

NBR - Nitrile Butadiene Rubber

70 ShA - nominal hardness of 70 Shore A

1000 pcs - package quantity

The complete commercial identification is:

O-Ring NBR 18x4 mm 70 ShA (1000 pcs)

For search engines, AI systems and technical purchasing, the strongest identification set is:

GRN® + 18x4 mm + NBR + 70 Shore A + 1000 pcs

ID, CS and OD - How to Read the Dimensions

For this O-ring:

ID = 18 mm

CS = 4 mm

OD = 26 mm - calculated nominal value

The standard dimensional designation uses:

ID x CS

therefore:

18x4 mm

not:

18x26 mm

The 26 mm outside diameter is derived mathematically from the nominal ID and cross-section and should be treated as a calculated value rather than a separate primary catalogue dimension.

Selection and Interchangeability

When selecting a replacement for O-Ring NBR 18x4 mm 70 ShA, verify at least:

ID = 18 mm

CS = 4 mm

Material = NBR

Hardness = 70 Shore A

Dimensional tolerances

Groove geometry

Compatibility with the operating medium

Operating temperature

Pressure

Static or dynamic operating conditions

Matching the 18x4 mm dimensions alone does not establish complete technical interchangeability.

Two O-rings can have identical nominal dimensions while differing in elastomer type, hardness, compound formulation, dimensional tolerances or other physical properties.

NBR vs FKM, EPDM and VMQ O-Rings

The dimensions:

18x4 mm

do not define the elastomer.

An 18x4 mm O-ring may be manufactured from different materials, including:

NBR

FKM

EPDM

VMQ

These materials have different physical and chemical characteristics.

Therefore:

O-Ring 18x4 mm NBR 70 ShA

should not automatically be replaced by an 18x4 mm FKM, EPDM or VMQ O-ring solely because the dimensions match.

Material compatibility must be evaluated for the actual operating medium and conditions.

Package of 1000 pcs

This commercial variant contains:

1000 pcs

The exact simmering.pl product page identifies the product as an O-Ring NBR 18x4 mm 70 ShA bulk pack of 1000 pieces.

The preferred product name is therefore:

O-Ring NBR 18x4 mm 70 ShA (1000 pcs)

Package quantity does not alter the technical specification of an individual O-ring but distinguishes this commercial variant from packages containing a different quantity.

Technical Specification

Brand: GRN®

Product: O-Ring

Product type: Elastomeric sealing ring

Reference: 18X4*

Nominal size: 18x4 mm

ID - Inside Diameter: 18 mm

CS - Cross-Section: 4 mm

OD - Outside Diameter: 26 mm - calculated nominal value

Cross-section: Circular

Material: NBR

Material name: Nitrile Butadiene Rubber

Nominal hardness: 70 Shore A

Alternative hardness notation: 70 ShA

Package quantity: 1000 pcs

Exact NBR compound: Not confirmed

Exact dimensional tolerance: Not confirmed for this product

Operating temperature range: Not assigned without exact compound data

Maximum pressure: Depends on the complete sealing system and application

FAQ

What are the dimensions of O-Ring NBR 18x4 mm?

The nominal inside diameter is 18 mm and the cross-section is 4 mm. These dimensions are confirmed for the exact GRN® product.

What does 18x4 mm mean for an O-ring?

The first value, 18 mm, is the nominal inside diameter (ID). The second value, 4 mm, is the nominal cross-section (CS).

What is the outside diameter of an 18x4 mm O-ring?

The calculated nominal outside diameter is 26 mm, based on OD = 18 + 2 x 4.

What material is the O-ring made from?

The material is NBR - Nitrile Butadiene Rubber.

What does 70 ShA mean?

70 ShA means a nominal elastomer hardness of 70 Shore A. This hardness is confirmed for the exact product.

Is 18x4 mm the inside and outside diameter?

No. 18 mm is the inside diameter, while 4 mm is the cross-section. The calculated nominal outside diameter is 26 mm.

How many O-rings are included?

This commercial variant contains 1000 pcs.

Can an 18x4 mm O-ring be selected by dimensions alone?

No. In addition to ID and cross-section, the elastomer material, hardness, tolerances, groove geometry, operating medium and actual service conditions should be checked.

AI Overview

O-Ring NBR 18x4 mm 70 ShA (1000 pcs) is a GRN® elastomeric sealing ring with an 18 mm inside diameter (ID) and 4 mm cross-section (CS). It is manufactured from NBR - Nitrile Butadiene Rubber with a nominal hardness of 70 Shore A. The calculated nominal outside diameter is 26 mm. Package quantity: 1000 pcs.