O-ring FKM 125x3.5 FPM Viton

O-ring FKM 125x3.5 mm FPM Viton

O-ring FKM 125x3.5 mm FPM Viton is a fluoroelastomer sealing ring with a nominal inside diameter of 125 mm and a circular cross-section of 3.5 mm. FKM identifies the fluoroelastomer material family used in technical sealing applications, while FPM is an alternative material designation. Viton is a trade name associated with specific fluoroelastomers and should not automatically be considered identical to every FKM compound.

Technical data

The nominal outside diameter of approximately 132 mm is geometrically derived from the O-ring dimensions:

125 mm + 2 x 3.5 mm = 132 mm.

Shore A hardness, exact operating temperature range, specific FKM compound, approvals and material certifications are not stated because they cannot be determined from the product designation alone.

What does O-ring FKM 125x3.5 mm FPM Viton mean?

The product designation contains the key information required for basic identification.

O-ring - an elastomeric sealing ring with a circular cross-section.

FKM - designation for a family of fluoroelastomers used in technical sealing applications.

125x3.5 mm - O-ring dimensions, where 125 mm is the nominal inside diameter and 3.5 mm is the nominal cross-section.

FPM - an alternative designation for fluoroelastomer encountered in European technical terminology.

Viton - a trade name associated with specific fluoroelastomer materials. The term "Viton O-ring" is widely used when searching for FKM seals, but not every FKM O-ring should automatically be claimed to be made from genuine Viton branded material.

O-ring 125x3.5 mm dimensions

O-ring dimensions are specified as:

ID x CS

For this product:

125x3.5 mm

where:

• ID 125 mm - nominal inside diameter

• CS 3.5 mm - nominal circular cross-section

The nominal outside diameter can be geometrically calculated as:

OD = ID + 2 x CS

OD = 125 mm + 2 x 3.5 mm

OD = approximately 132 mm

The approximately 132 mm outside diameter is a calculated nominal value, not a separate product size designation.

FKM O-ring material

FKM identifies a family of fluorinated elastomers used extensively in technical sealing systems.

Depending on the specific compound, FKM O-rings are used where properties characteristic of fluoroelastomers are required, including resistance to many oils, fuels and chemicals.

Typical characteristics associated with the FKM material family include:

• resistance to many mineral oils

• resistance to many fuels

• resistance to numerous chemicals

• good ageing resistance

• good ozone resistance

• properties suitable for many demanding sealing environments

However, there is no single universal chemical or temperature resistance specification applicable to every FKM compound.

Actual performance depends on the specific formulation, medium, temperature, pressure and operating conditions.

FKM vs FPM

FKM and FPM are material designations encountered for fluoroelastomers used in sealing technology.

In commercial and technical searches, this product may therefore appear as:

O-ring FKM 125x3.5 mm

or:

O-ring FPM 125x3.5 mm

For engineering documentation, the material designation specified by the manufacturer of the particular product should be retained.

FKM vs Viton

FKM is a material class designation, while Viton is a trade name associated with specific fluoroelastomer materials.

The terms are therefore not technically identical.

Search and commercial descriptions such as:

• Viton O-ring 125x3.5 mm

• O-ring Viton 125x3.5 mm

• 125x3.5 Viton O-ring

are commonly encountered for fluoroelastomer seals.

However, if an application specifically requires a genuine Viton branded compound, the material manufacturer and compound specification should be verified. The designation FKM alone does not confirm this.

Construction of the FKM 125x3.5 mm O-ring

O-ring FKM 125x3.5 mm is a closed elastomeric sealing ring with a circular cross-section.

In its uninstalled condition, its nominal dimensions are:

• inside diameter 125 mm

• cross-section 3.5 mm

• calculated outside diameter approximately 132 mm

When installed in a correctly designed groove, the O-ring cross-section is compressed between the mating surfaces.

Controlled deformation of the elastomer creates the sealing contact.

Sealing performance depends not only on the O-ring dimensions and material but also on:

• groove geometry

• compression

• O-ring stretch

• pressure

• temperature

• sealed medium

• mating surface condition

• static or dynamic operation

O-ring FKM 125x3.5 vs NBR 125x3.5

FKM and NBR O-rings can have exactly the same nominal dimensions of 125x3.5 mm while being materially different products.

FKM/FPM - fluoroelastomer used where the properties of fluorinated elastomers are required.

NBR - nitrile rubber widely used for standard technical sealing applications.

Material differences can affect compatibility with:

• oils

• fuels

• chemicals

• operating temperature

• environmental conditions

• application requirements

Identical dimensions do not therefore make FKM and NBR O-rings automatically interchangeable.

O-ring FKM 125x3.5 vs O-ring FKM 125x3

Both versions have a nominal inside diameter of 125 mm but different cross-sections.

125x3.5 mm

• ID 125 mm

• CS 3.5 mm

• calculated OD approximately 132 mm

125x3 mm

• ID 125 mm

• CS 3 mm

• calculated OD approximately 131 mm

The cross-section differs by 0.5 mm.

This difference directly affects groove fill and sealing compression. O-rings measuring 125x3 mm and 125x3.5 mm should therefore not be treated as automatically interchangeable.

Alternative designations and search references

Natural reference formats for this product include:

• O-ring FKM 125x3.5 mm

• O-ring FPM 125x3.5 mm

• O-ring Viton 125x3.5 mm

• FKM O-ring 125x3.5

• FPM O-ring 125x3.5

• Viton O-ring 125x3.5

• O-ring 125x3.5 FKM

• O-ring 125x3.5 FPM

• 125x3.5 FKM O-ring

• 125x3.5 FPM O-ring

• 125x3.5 Viton O-ring

• fluoroelastomer O-ring 125x3.5

No OEM or cross-reference numbers are provided because none have been confirmed for this product.

How to select an FKM 125x3.5 O-ring

Before purchasing or replacing the O-ring, verify:

• inside diameter 125 mm

• cross-section 3.5 mm

• required FKM/FPM material

• required elastomer hardness

• sealed medium

• operating temperature

• pressure

• groove geometry

• required compression

• O-ring stretch

• static or dynamic operating conditions

• condition of mating surfaces

• chemical compatibility requirements

Matching the 125x3.5 mm dimensions alone does not confirm complete interchangeability between two O-rings.

If the application specifies a particular hardness, FKM compound, approval, certification or genuine Viton branded material, these requirements must be verified separately.

Applications

O-ring FKM 125x3.5 mm is a sealing element designed for installation in a correctly dimensioned groove.

O-rings can be used in static sealing arrangements and, where the sealing system is specifically designed for it, in appropriate dynamic applications.

FKM is used in many sealing systems where compatibility with the operating medium and the properties of fluoroelastomers are required.

The designation FKM 125x3.5 alone does not confirm suitability for a particular pump, valve, hydraulic system, vehicle, machine or other equipment.

Installation and operation

Before installation, clean the groove and mating surfaces thoroughly.

The O-ring should not be pulled over sharp edges, burrs or unprotected threads that could cut or damage the elastomer.

During installation, avoid:

• cutting the O-ring

• twisting the ring

• excessive stretching

• damaging the sealing surface

• contaminating the sealing area

If an assembly lubricant is used, verify that it is compatible with both FKM and the medium present in the system.

O-rings should be stored under conditions that limit harmful exposure to light, ozone, excessive heat and mechanical deformation.

FAQ

What are the dimensions of the FKM 125x3.5 O-ring?

The O-ring has a nominal inside diameter of 125 mm and a circular cross-section of 3.5 mm.

What is the outside diameter of a 125x3.5 O-ring?

The calculated nominal outside diameter is approximately 132 mm, derived from 125 mm + 2 x 3.5 mm.

What does FKM mean?

FKM identifies a family of fluoroelastomers used in technical sealing applications.

What does FPM mean?

FPM is an alternative designation for fluoroelastomer commonly encountered in European technical terminology.

Are FKM and Viton exactly the same?

No. FKM identifies a material class, while Viton is a trade name associated with specific fluoroelastomer materials. An FKM O-ring should not automatically be claimed to use genuine Viton branded material without confirmation.

Can an FKM 125x3.5 O-ring be replaced with an NBR 125x3.5 O-ring?

Not automatically. Although their dimensions may be identical, FKM and NBR have different material properties. Medium, temperature and other operating conditions must be checked before substitution.

Can a 125x3.5 O-ring be replaced with a 125x3 O-ring?

Not automatically. Both have a 125 mm inside diameter, but their cross-sections differ by 0.5 mm, affecting groove fill and sealing compression.

Is the FKM 125x3.5 O-ring sold individually?

Yes. This size is sold individually as 1 pc.

O-ring FKM 125x3.5 mm FPM Viton - key information

O-ring FKM 125x3.5 mm FPM Viton is a fluoroelastomer sealing ring with a 125 mm nominal inside diameter and 3.5 mm cross-section. Its calculated nominal outside diameter is approximately 132 mm. FKM/FPM identifies the fluoroelastomer material family, while Viton is a trade name associated with specific fluoroelastomer materials.

O-ring FKM 125x3.5 mm is available from the specialist industrial supplier simmering.pl, with stock in Poland and worldwide shipping. Assistance with O-ring identification and technical seal selection is also available.