Bearing Suffix Guide: What C3, C4, ZZ, 2RS, NR, K and Other Bearing Codes Mean

When ordering or replacing a bearing, the basic bearing number is only part of the specification. A bearing marked 6205, 6205 C3, 6205 ZZ or 6205 2RS C3 may belong to the same basic bearing series, but the suffix can indicate important differences in internal clearance, sealing, shielding, mounting or accuracy.

Ignoring these suffixes can result in an incorrect bearing being selected even when the basic bearing number appears to be the same. For purchasing teams, workshops, maintenance engineers and bearing traders, understanding these codes helps reduce the risk of ordering the wrong specification.

Quick Reference: Common Bearing Suffix Codes

What Does C3 Mean on a Bearing?

C3 means the bearing has radial internal clearance greater than Normal.

Internal clearance is the small amount of movement available between the bearing rings and rolling elements before the bearing is operating. Clearance can change after installation because of shaft fits, housing fits, temperature differences and thermal expansion.

A C3 bearing therefore starts with more internal clearance than a Normal-clearance bearing. This can be necessary in applications where operating conditions are expected to reduce the effective clearance.

C3 vs C4 Bearings

Both C3 and C4 indicate greater-than-Normal radial internal clearance. C4 provides more clearance than C3.

C4 should not be viewed as an automatic upgrade from C3. The correct clearance depends on factors such as fit, operating temperature, load, speed and equipment-manufacturer requirements.

What Does ZZ Mean on a Bearing?

ZZ commonly indicates metal shields on both sides of a bearing. Some manufacturers use ZZ, while others commonly use 2Z.

Metal shields help retain lubricant and reduce the entry of larger contaminants. Because shields normally create less friction than contact seals, they can be suitable for applications where lower friction and higher rotational speed are important.

However, shields do not provide the same level of protection against moisture and fine contamination as many contact-seal designs.

What Does 2RS Mean on a Bearing?

2RS commonly refers to seals on both sides of the bearing.

Sealed bearings generally provide stronger protection against contamination and moisture than shielded bearings. Depending on the seal design, they can also generate more friction than shielded versions.

Manufacturer terminology varies. Depending on the brand and bearing series, codes such as 2RS, 2RS1, 2RSH, LLU or DDU may be encountered.

ZZ vs 2RS: What Is the Difference?

A 6205 ZZ and a 6205 2RS may have the same basic dimensions, but this does not automatically make them suitable substitutes for one another.

What Does NR Mean on a Bearing?

NR commonly identifies a bearing with a snap-ring groove and a snap ring.

A related suffix is N, which generally indicates the snap-ring groove without the snap ring.

These features can help locate the bearing axially in a housing. Therefore, 6205 and 6205 NR should not automatically be treated as identical items.

What Does K Mean on a Bearing?

K commonly indicates a tapered bore, frequently with a taper of 1:12.

On applicable bearing series, K30 can identify a tapered bore with a 1:30 taper.

Tapered-bore bearings may be mounted using adapter sleeves, withdrawal sleeves or tapered shaft seats. For this reason, a K-suffix bearing should not automatically replace the equivalent cylindrical-bore version without checking the mounting arrangement.

What Do P5 and P6 Mean?

P5 and P6 are commonly associated with higher bearing tolerance or accuracy classes.

These specifications can be important in machinery where running accuracy, shaft precision, vibration or rotational performance is critical.

A standard bearing may have similar dimensions but may not satisfy the accuracy requirements of an application that specifically requires P5 or P6.

Can Bearings With the Same Basic Number Be Different?

Yes. Consider the following examples:

The basic designation remains similar, but the complete specification can be different because of changes in clearance, sealing, shielding or mounting features.

This is why purchasing teams should avoid matching bearings using only the basic number.

Are Bearing Suffixes the Same Across SKF, JTEKT/KOYO, NSK, NTN, FAG and NACHI?

No. Many concepts are similar across manufacturers, but the exact designation system can vary.

For example, one manufacturer may use ZZ for shields on both sides while another may use 2Z. Seal and cage designations can vary even more.

When comparing brands such as SKF, JTEKT / KOYO, TIMKEN, NACHI and FAG, the correct approach is to compare the technical characteristics represented by the suffix rather than simply matching the letters.

How to Order the Correct Bearing

When sending a bearing enquiry, provide the complete designation whenever possible.

You can also explore our Bearings & Housings range for industrial and automotive applications.

Frequently Asked Questions

Technical note: Bearing suffix meanings can vary by manufacturer, bearing type and product series. This guide provides common industry interpretations and should not replace the manufacturer’s official catalogue or application-specific engineering recommendation.