The 608 is the most-used miniature ball bearing on the planet. You'll find it in skateboards, inline skates, electric fans, small DC motors, 3D printers, fishing reels and power tools. The base dimensions are always the same: 8 mm bore × 22 mm outer diameter × 7 mm width.
But the seal configuration changes everything. The two variants you'll see most are 608ZZ (metal shields) and 608-2RS (rubber seals). They are not interchangeable in every application — and choosing the wrong one will cost you either speed or bearing life.
What is 608ZZ?
The "ZZ" means two metal shields, one on each side. The shields are pressed into the outer ring and sit very close to the inner ring, but they do not touch. They block most dust and large debris by geometry, but they are not a true seal.
- Lower friction — less drag, slightly higher top speed
- Not watertight — fine dust and liquids can enter
- Often relubricable — some ZZ variants have a removable shield for cleaning and re-greasing
- Typical use: clean indoor applications, high-speed fans, precision spindles, equipment where you can control the environment
What is 608-2RS?
The "2RS" means two rubber seals (RS = Rubber Seal), one on each side. Unlike metal shields, the rubber lip physically contacts the inner ring. This creates a true barrier against contaminants.
- Higher friction — the rubber lip adds drag, so top speed is slightly lower
- Watertight and dust-tight — blocks water, mud, dust and most chemicals
- Sealed for life — the factory grease stays in, contaminants stay out, you don't relubricate
- Typical use: skateboards, outdoor equipment, wet or dusty environments, anything you don't want to service regularly
Quick decision guide
| If your application is... | Choose | Why |
|---|---|---|
| Indoor, clean, high-speed (fan, spindle, 3D printer) | 608ZZ | Less drag, more speed |
| Outdoor, wet, dusty (skateboard, scooter, garden tool) | 608-2RS | Seals out water and grit |
| You want to clean and re-grease regularly | 608ZZ | Removable shield, serviceable |
| You want fit-and-forget, no maintenance | 608-2RS | Sealed for life |
| High humidity or chemical exposure | 608-2RS | Rubber seal resists liquids |
What about 608 (open, no seals)?
You'll also see plain 608 with no suffix. This is an open bearing — no shields, no seals. Lowest friction of all, but zero contamination protection. Only suitable for fully enclosed, clean, well-lubricated assemblies. Most buyers should not choose this variant unless they have a specific reason.
Need help specifying?
Send us your application details — what the bearing runs in, the speed, the environment, how often you can service it — and we'll recommend ZZ, 2RS, or a hybrid option based on real engineering, not a guess.