A seal or shield decides three things at once: how much contamination reaches the raceway, how much friction the bearing adds, and how fast it can run. The letters after the model number are therefore the most consequential part of a bearing designation, and the part most often changed without checking the consequence.
There are two families. A shield is a pressed steel disc with a small gap to the inner ring: nothing rubs, so speed and torque stay close to an open bearing, but the gap also lets fine dust and water through. A seal is a rubber lip that either touches the inner ring (contact) or sits in a narrow gap (non-contact). Contact seals protect best and cost the most in friction; non-contact seals sit between the two.
The practical question is not which seals best, but which protects enough for the environment while still leaving speed and temperature headroom. A 2RS bearing in a 12,000 rpm motor will fail from lip burn long before it fails from contamination. The tables on each page below give the numbers for that decision.
| Designation | Construction | Contact | Dust | Water splash | Speed vs open | Typical use |
|---|---|---|---|---|---|---|
| Open | No seal or shield | — | None | None | 100% | Oil-lubricated, enclosed housings |
| 2Z / ZZ | Pressed steel shield, both sides | No | Coarse | No | 85–95% | Motors, gearboxes, high speed |
| 2RZ | Rubber lip in a narrow gap, both sides | No | Fine | Light | 80–90% | VFD motors, high-speed pumps |
| 2RS / 2RS1 | Rubber lip on the inner ring, both sides | Yes | Tight | Yes | 60–70% | Dusty, damp, sealed-for-life |
| RSH / 2RSH | Sheet-steel reinforced rubber lip | Yes | Tight | Yes | 60–70% | Large bore sizes, heavier lips |
| FKM seal | Fluorocarbon rubber lip | Yes | Tight | Yes | 55–70% | 120–200 °C positions |
| PTFE lip | PTFE sealing lip | Yes | Tight | Yes | 60–75% | 200–260 °C, chemical duty |
| Low-torque seal | Thin non-contact lip | No | Fine | Light | 85–92% | Small motors, instruments |
The default choice for dusty, damp or sealed-for-life positions at moderate speed.
Read →The choice when speed and temperature matter more than fine dust.
Read →The compromise suffix: sealing close to 2RS, friction close to 2Z.
Read →For oil-lubricated, enclosed positions where the housing does the sealing.
Read →Five codes, one construction — and the details that are not interchangeable.
Read →The heavy-duty version of the contact seal, for big shafts and stiff lips.
Read →Where standard nitrile seals harden, crack and let the grease escape.
Read →For gearmotors, battery devices and instruments where friction is the design constraint.
Read →C1 to C5: how much play the bearing is built with, and why C3 is the motor default.
Read →P0 to P2 and the ABEC crosswalk: what tolerance actually buys you.
Read →Steel, brass, polyamide and phenolic — the part that sets high-speed limits.
Read →Grease, oil and solid lubricants, and where each one stops working.
Read →Neither is better in general. 2RS seals against dust and splash but gives up 30–40% of the speed rating and adds drag; 2Z keeps nearly the full speed rating but only stops coarse dirt. Choose by environment first, then check that the speed rating still covers the application.
A standard 2RS bearing is greased for life and cannot be relubricated without destroying the seal. If the duty cycle needs relubrication, use an open or shielded bearing in a housing with a grease nipple, or specify a bearing with a relubrication groove.
Nothing to do with the number of seals. 2RS1 is SKF's design variant of a contact rubber seal reinforced with sheet steel; both sides are sealed. FAG calls the same construction 2RSR, NSK DDU and NTN LLU.
No. A contact seal is dust-tight and splash-resistant, not immersion-rated. For immersion or pressure washing you need a housed unit with a separate labyrinth or a mechanical seal, not a standard 2RS bearing.
Tell us the application — speed, load, temperature and environment — and we will name the seal, clearance, class and cage that fit it.