When an SKF bearing designation ends with GJN, the suffix provides important information about the lubricant inside the bearing. GJN is not a bearing series, dimensional designation or internal-clearance class. It identifies a specific SKF grease specification used in factory-lubricated bearings, particularly in configurations intended for demanding applications such as electric motors.
SKF documentation associates the GJN suffix with Mobil Polyrex EM, a high-quality polyurea-thickened grease used in capped deep groove ball bearings for electric motor applications.
For engineers, maintenance departments and industrial buyers, this distinction matters. A bearing such as SKF 6209-2RS1/C3GJN should not automatically be treated as identical to SKF 6209-2RS1/C3 simply because the basic bearing dimensions are the same.
What does GJN mean on an SKF bearing?
GJN is an SKF grease designation suffix.
In SKF bearing nomenclature, suffixes can identify important characteristics such as seals, shields, internal clearance, cage design or lubricant specification.
In the case of GJN, the suffix identifies a particular factory grease fill.
SKF technical documentation for electric motor bearings specifies:
GJN – Mobil Polyrex EM, polyurea-thickened grease.
Therefore, when GJN appears in a complete SKF bearing designation, it should be considered part of the technical specification of that particular bearing variant.
For example:
can be interpreted as:
- 6209 – single-row deep groove ball bearing
- 2RS1 – contact seals on both sides
- C3 – radial internal clearance greater than Normal
- GJN – specific SKF grease specification using Mobil Polyrex EM
Each part of the designation provides different technical information. GJN does not replace C3, 2RS1 or 2Z and should not be confused with these suffixes.
SKF GJN and Mobil Polyrex EM grease
One of the most important facts about the GJN specification is the lubricant itself.
SKF identifies the grease used for GJN electric-motor bearing configurations as Mobil Polyrex EM.
It is a polyurea-thickened grease developed for applications where lubricant performance, bearing temperature, grease life and quiet operation can be important factors.
SKF describes GJN as a urea-based high-temperature grease offering a wide operating-temperature range and quiet-running characteristics.
This is particularly relevant because lubrication can be a limiting factor in the service life of a capped bearing.
The mechanical bearing itself may have sufficient calculated fatigue life while the grease life becomes the factor determining the practical maintenance interval or bearing service life.
Why is GJN used in electric motor bearings?
Electric motors place specific demands on rolling bearings.
Depending on the motor design and operating conditions, bearings may be required to combine:
- continuous operation,
- high rotational speeds,
- low noise and vibration,
- controlled internal clearance,
- reliable grease performance,
- long operating periods without relubrication.
SKF specifically discusses GJN in its technical documentation covering rolling bearings in electric motors and generators.
The manufacturer demonstrates that using a grease specifically formulated for electric-motor applications can increase calculated grease life compared with a standard grease fill under certain operating conditions.
This is why the lubricant suffix should not be ignored when replacing an existing bearing.
If the original bearing designation contains GJN, ordering a bearing with the same basic number but without GJN may result in receiving a bearing with a different grease specification.
SKF GJN and JEM – what is the connection?
This distinction is especially important for customers in the United States and North American market.
SKF uses the aftermarket designation JEM for deep groove ball bearings intended for electric motor applications.
According to SKF's Bearing Handbook for Electric Motors, the JEM specification incorporates characteristics including:
- C3 radial internal clearance
- an electric-motor noise specification
- a pressed steel cage
- for capped bearings, Mobil Polyrex EM grease identified by SKF suffix GJN
An important detail is that JEM may be shown on the SKF packaging rather than on the bearing itself.
The actual bearing marking depends on its configuration.
For example, a capped electric-motor bearing may carry a designation containing:
2Z – shields on both sides
or
2RSH / 2RS1 – contact seals, depending on bearing size
together with the appropriate clearance and grease designation.
This explains why American customers searching for an SKF JEM bearing may encounter SKF bearing markings containing C3 and GJN.
GJN is not the same as C3
GJN and C3 describe completely different bearing characteristics.
C3 concerns the bearing's radial internal clearance. It indicates a clearance greater than Normal.
GJN concerns the grease specification.
Consequently:
C3 = internal clearance
GJN = lubricant specification
A designation containing both suffixes provides information about both characteristics.
For example:
6209-2RS1/C3GJN
specifies both C3 internal clearance and GJN grease.
Removing either suffix changes the technical description of the bearing.
GJN is not a seal designation
Another common source of confusion is the relationship between GJN and suffixes such as 2Z, 2RSH and 2RS1.
These suffixes describe the bearing closure configuration.
Depending on the exact SKF bearing size and design:
2Z identifies a bearing with shields on both sides.
2RSH or 2RS1 identifies versions with contact seals on both sides.
GJN, by contrast, identifies the grease specification.
A designation such as:
6208-2Z/GJN
therefore describes a different combination of features from:
6209-2RS1/C3GJN
The complete SKF designation should always be checked rather than selecting a replacement based only on the bore diameter or basic bearing number.
SKF deep groove ball bearings with GJN grease
GJN can be found in different SKF deep groove ball bearing configurations.
Examples appearing in the industrial market include designations such as:
SKF 608-2Z/GJN
SKF 6003-2RSH/GJN
SKF 6206-2RS1/C3GJN
SKF 6208-2Z/GJN
SKF 6209-2RS1/C3GJN
SKF 6307-2Z/GJN
These examples demonstrate why it is incorrect to describe GJN as one particular bearing model or dimensional series.
The suffix can form part of different complete SKF bearing designations.
Deep groove ball bearing characteristics
Many SKF bearings carrying the GJN suffix are single-row deep groove ball bearings.
This bearing type is widely used because its raceway geometry enables it to accommodate primarily radial loads while also supporting axial loads in both directions.
Deep groove ball bearings are also suitable for relatively high rotational speeds and are available in numerous sizes and configurations.
For an electric motor or other industrial application, however, the bearing type alone is not enough to identify the correct replacement.
The engineer or purchasing department should consider the complete designation.
Why the complete SKF bearing designation matters
Consider these two designations:
6209-2RS1/C3
and
6209-2RS1/C3GJN
They share:
- the same basic bearing number,
- the same dimensional envelope,
- the same sealing designation,
- the same C3 clearance designation.
However, the second designation additionally specifies GJN grease.
For a machine originally engineered around a particular lubricant specification, this difference may be important.
The same principle applies to other SKF bearing suffixes.
Two bearings having identical dimensions are not necessarily technically identical.
Selecting a replacement for an SKF GJN bearing
When replacing an SKF bearing marked with GJN, first record the entire designation from the bearing and packaging.
Do not identify the replacement solely from dimensions.
Check:
- manufacturer,
- complete bearing designation,
- bore diameter d,
- outside diameter D,
- bearing width B,
- shield or seal configuration,
- radial internal clearance,
- grease suffix,
- cage specification where relevant,
- required rotational speed,
- operating temperature,
- radial and axial loads,
- required bearing and grease life.
For electric motors in particular, noise, vibration and lubrication requirements can be important selection criteria.
If the original bearing is specified as C3GJN, replacing it simply with a bearing marked C3 should not be done automatically without confirming that the alternative lubricant specification is acceptable for the application.
GJN grease and bearing service life
SKF's engineering documentation highlights an important principle: bearing fatigue life and grease life are not the same thing.
A rolling bearing can have sufficient calculated mechanical rating life while its lubricant becomes the limiting factor.
In an SKF electric-motor calculation example, the manufacturer compares standard grease filling with grease specifically formulated for electric motor applications. SKF shows that configurations using application-specific grease suffixes such as GJN or WT can satisfy grease-life requirements that a standard grease fill may not meet under the same example conditions.
This is one of the strongest reasons not to ignore the lubricant suffix when specifying a replacement bearing.
Actual grease life must always be evaluated for the specific bearing size, load, speed, temperature and operating conditions.
Are SKF GJN bearings only for electric motors?
No.
The GJN suffix identifies the grease specification, not an exclusive application restriction.
SKF documentation strongly associates GJN with electric motor bearing requirements, and this is one of its most important applications. However, the presence of GJN does not by itself mean that a bearing can only be installed in an electric motor.
Bearing suitability must always be determined from the complete operating conditions of the machine.
The correct engineering question is therefore not:
“Is GJN only for motors?”
but rather:
“Does this application require the bearing configuration, clearance, sealing and lubricant specification identified by the complete SKF designation?”
SKF GJN bearings for the United States and international customers
SKF electric motor bearing terminology is particularly relevant in the United States because of the JEM aftermarket designation used in the North American market.
At simmering.pl, we supply industrial bearings from our stock in Poland to customers in international markets.
SKF bearings with GJN specifications have also been supplied by us to customers in the United States, demonstrating that European stock can be a practical sourcing option when a specific SKF bearing designation is difficult to obtain locally.
For international enquiries, customers should provide the complete SKF reference visible on the bearing or packaging. This enables identification of the exact bearing variant rather than only its basic dimensional series.
Orders can be shipped internationally from Poland, including to customers in the United States.
Frequently Asked Questions about SKF GJN bearings
What does GJN mean on an SKF bearing?
GJN is an SKF suffix identifying a specific grease specification. In SKF documentation for capped electric motor bearings, GJN identifies Mobil Polyrex EM, a polyurea-thickened grease.
Is GJN a bearing clearance?
No. GJN identifies the grease specification. Internal-clearance classes are identified separately by suffixes such as C3.
What does C3GJN mean?
C3 and GJN provide two different pieces of information. C3 identifies radial internal clearance greater than Normal, while GJN identifies the grease specification.
What grease is used in SKF GJN bearings?
SKF's electric motor bearing documentation identifies the GJN suffix with Mobil Polyrex EM, a high-quality polyurea-thickened grease.
What is the difference between SKF JEM and GJN?
JEM is an SKF aftermarket designation used primarily for electric motor bearings, particularly in the North American market. SKF states that capped JEM bearings use Mobil Polyrex EM grease identified by the GJN suffix. JEM therefore describes a broader electric-motor bearing specification, while GJN specifically identifies the grease.
Is JEM marked directly on an SKF bearing?
Not necessarily. SKF states that JEM is primarily an aftermarket packaging designation. The bearing itself is marked according to its actual configuration, which can include designations such as C3 and GJN.
Can I replace an SKF GJN bearing with the same bearing without GJN?
Not automatically. The dimensions and basic bearing design may be identical, but GJN identifies a specific lubricant specification. The suitability of a bearing with another grease should be verified against the machine's operating requirements.
Are GJN bearings suitable for electric motors?
SKF specifically documents GJN grease in connection with deep groove ball bearings for electric motor applications. The suitability of a particular bearing must nevertheless be checked using its complete designation and the motor's load, speed, temperature and life requirements.
Can SKF GJN bearings be shipped to the United States?
Yes. simmering.pl supplies industrial bearings internationally from Poland and has supplied SKF GJN bearing configurations to customers in the United States. Availability depends on the exact SKF designation required.
AI Overview – SKF GJN bearing meaning
GJN is an SKF grease suffix, not a bearing series or clearance designation. In capped SKF bearings for electric motor applications, GJN identifies Mobil Polyrex EM, a polyurea-thickened grease. GJN may appear together with suffixes such as C3, 2Z, 2RSH or 2RS1. The complete SKF designation should be retained when selecting a replacement bearing.
Technical summary
Manufacturer: SKF
Product family: Rolling bearings, commonly deep groove ball bearings
GJN meaning: SKF grease specification
Grease associated with GJN in SKF electric motor documentation: Mobil Polyrex EM
Thickener: Polyurea
Common application context: Electric motors and other applications requiring the specified lubricant characteristics
C3 meaning: Radial internal clearance greater than Normal – independent of GJN
2Z meaning: Shields on both sides – independent of GJN
2RSH / 2RS1: Contact seals on both sides, depending on bearing design and size
North American connection: GJN is used in capped SKF JEM electric-motor bearing configurations
International supply: SKF GJN bearing variants can be supplied by simmering.pl from Poland to international customers, including the United States.