2RS vs ZZ Seals
The same bearing is usually sold in three forms: open, shielded (ZZ or 2Z), and sealed (2RS). Open, shielded and sealed versions may share nominal boundary dimensions within a manufacturer’s size family. Confirm the exact designation, dimensions and equipment requirements before selecting a replacement.
ZZ — Metal Shields
A shield is a thin steel disc fixed to the outer ring, sitting very close to the inner ring without touching it. The non-contact shield avoids seal-lip rubbing, but bearing and lubricant friction still generate heat. Use the exact product’s speed and lubrication data.
Shields keep out solid contamination — dust, grit, swarf. They do not keep out water, and they will not hold grease in against pressure washing.
2RS — Rubber Seals
A contact seal commonly uses an elastomer lip to help exclude contamination and retain grease. Seal materials and contact geometry vary; manufacturers also offer non-contact and low-friction sealed designs. Ordinary contact seals should not be assumed to withstand pressure washing; protection depends on the specific seal and housing design.
The cost is friction. A contact seal generates drag and heat, which lowers the speed the bearing can safely run at and raises its running temperature.
Side by Side
| ZZ / 2Z (shielded) | Typical contact-sealed design (verify the exact suffix) | |
|---|---|---|
| Contact with inner ring | No | Yes |
| Friction and heat | Minimal | Noticeably higher |
| Maximum speed | Check the exact product rating | Check the exact seal variant rating |
| Keeps out dust | Good | Better |
| Water exposure | Not a watertight closure | Protection depends on the seal and housing; check manufacturer guidance |
| Retains grease | Adequate | Excellent |
| Temperature limit | Check lubricant, cage and product limits | Also check the exact seal material and product limits |
| Relubrication | Follow the manufacturer’s service instructions | Follow the manufacturer’s service instructions; do not assume closure removal is permitted |
Manufacturer Sources
SKF explains its low-friction and contact seal designs, including why protection and friction depend on the seal geometry and bearing size. The article is dated August 2003 and does not establish current product availability. The NSK designation guide separately identifies shielded, contact-sealed and non-contact-sealed configurations. Use the current exact product record for selection.
Which Should You Use?
Consider a shielded design where the specified speed, lubrication and contamination conditions permit it — electric motors, fans, indoor machinery, spindles, equipment that runs continuously in a controlled space.
Consider an appropriate sealed design where contamination protection is required — bicycle and motorcycle wheels, agricultural and garden machinery, pumps, outdoor equipment, equipment exposed to contamination, subject to the exact seal and housing specifications.
Start with the machine’s specified closure, lubricant and speed requirements. A generic 2RS label does not establish suitability for washdown, temperature extremes or high speed. For pressure washing, check the manufacturer’s specific sealing solution rather than assuming all rubber-sealed bearings are waterproof.
What About Open Bearings?
Open bearings have neither, and rely on the housing to keep contamination out and lubricant in. They suit sealed gearboxes and oil-bath applications where the assembly is already protected, and they allow the machine’s own circulating oil to reach the bearing.
Are They Interchangeable?
Some open, shielded and sealed 6205 products share a 25 × 52 × 15 mm envelope. Check the exact manufacturer’s dimensions, tolerances and mounting requirements; shared nominal size alone does not establish interchangeability. Functionally they are not equivalent, and substituting one for another changes the speed limit, the running temperature and the protection level. If a machine was specified with seals, there is usually a reason.
Note also that a seal or shield does not change internal clearance. Those are separate suffixes and are chosen independently — see how to read bearing numbers for the full list.
Find dimension records and review source status for sealed or shielded candidates in our cross reference database.
Related: 6205 Bearing Selection and Manufacturer Evidence — Review manufacturer dimension records, full designations and the checks needed before comparing replacements.
Shopping for a specific size? See our 6304 buying guide or 6205 brand comparison — both cover 2RS and ZZ options for that specific bearing size.