Industrial MRO Reference Library · Technical Reference

Shields vs Seals — ZZ, 2RS & Variants

Shields and seals close off the sides of a bearing to hold grease in and keep dirt out. This sheet explains the difference between metal shields and rubber seals and decodes the suffixes different brands use for them.

Ref MRO-0003ISO 15

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

A shield is a pressed metal plate fixed in the outer ring that comes close to, but does not touch, the inner ring. It keeps out larger particles and holds grease in with very little drag. A seal is a rubber lip, usually nitrile molded onto a steel insert. A contact seal rubs on the inner ring and gives the best protection against dust and moisture, but adds friction and heat, so it limits speed. A non-contact seal has a rubber lip with a small gap, and sits between a shield and a contact seal in protection and speed. Bearings with two closures are normally greased for life. ISO 15 sets the boundary dimensions, which closures do not change, but suffix codes are set by each maker.

How to identify

Look at the side of the bearing. Bright or plain metal plates held by a snap wire or crimp are shields. A black, brown or colored rubber face is a seal. Read the suffix after the basic number. A single letter or code means one side is closed. A "2" or doubled letter usually means both sides.

Suffix decoder

Closure	Common generic suffix	Brand variants seen	Notes
One metal shield	Z	Z	One side open
Two metal shields	ZZ or 2Z	ZZ, 2Z, -2Z	Non-contact; good for higher speed
One contact rubber seal	RS	RS, RS1, RSR, DU, LU	One side open
Two contact rubber seals	2RS	2RS, 2RS1, 2RSR, DDU, LLU	Best general protection, more drag
Two non-contact rubber seals	2RZ	2RZ, VV, LLB	Lower drag than contact seals
Two low-friction contact seals	Varies	2RSL, LLH	Brand-specific designs
Open	No closure suffix	None	Lubricated by the machine or by the fitter

Key points

Closures do not change the bore, OD or width. A 6205, 6205-ZZ and 6205-2RS fit the same housing.
Contact seals limit speed. Check the maker's limiting speed before switching from shields to seals on a fast shaft.
In washdown or dusty service, a contact seal usually lasts longer than a shield.
Suffix codes are not universal. Confirm the closure type with the brand's designation guide when cross-referencing.
A sealed bearing cannot be re-greased in place. If the machine has a grease fitting at that bearing, it may need an open or single-shield bearing.

Common mistakes

Treating ZZ and 2RS as interchangeable in a wet or dirty application.
Fitting a contact-sealed bearing on a high-speed spindle that was designed for shields.
Assuming a code means the same in two brands.
Greasing a sealed bearing through a fitting until the seal pops out.

Governing standards: ISO 15 (radial bearing boundary dimensions). Manufacturer designation guides for closure suffixes.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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