Mini roller skate bearings have a smaller outer diameter than standard 608 bearings. The key difference between 608 and 688 is their outer size and width: both have an 8 mm axle hole, but they do not fit the same wheel seat without a compatible adapter.
Check both the axle and the wheel before ordering. A bearing that fits your axle can still be the wrong size for your wheel.
Compare the bearing dimensions
The bore is the hole through the centre of the bearing. The outer diameter must match the wheel's bearing seat, and the width must suit the complete installation.
| Bearing | Bore | Outer diameter | Width |
|---|---|---|---|
| 608 | 8 mm | 22 mm | 7 mm |
| 627 | 7 mm | 22 mm | 7 mm |
| 688 mini | 8 mm | 16 mm | 5 mm |
| Bont 167 mini | 7 mm | 16 mm | Confirm for the complete setup |
The Bont 167 product information confirms its 7 mm bore and 16 mm outer diameter. Confirm the width and spacer requirements for your intended setup before fitting it.
The difference between 608 and 688
A 608 bearing is 22 mm across its outside, while a 688 mini bearing is 16 mm. The 688 is also narrower. Sharing an 8 mm bore does not make the two formats interchangeable.
If your wheel is designed for standard 608 bearings, an unadapted 688 will not fill the bearing seat. If the wheel is designed for a 16 mm mini bearing, a 608 is too large for that seat. Check the wheel specification rather than assuming you can transfer your existing set.
Choose for a 7 mm or 8 mm axle
For a standard 22 mm wheel seat, 608 bearings suit 8 mm axles and 627 bearings suit 7 mm axles. For a compatible 16 mm mini seat, Bont 688 bearings suit 8 mm axles and Bont 167 bearings suit 7 mm axles.
Check your plate or axle specification if you are unsure of the axle diameter. Do not choose a bearing simply because it is described as a roller skate bearing or a mini bearing.
How mini bearing adapters work
The Bont 167 and 688 adapter fits around a compatible mini bearing so it can be used in a standard 608-size wheel seat. You need one adapter for each bearing.
The adapter changes how the outside of the bearing fits the wheel. It does not change the bearing's axle hole. A 167 bearing with an adapter still requires a 7 mm axle; a 688 still requires an 8 mm axle.
Confirm the bearing, adapter, wheel and any spacer as a complete setup. An outer diameter match alone does not establish that the installation is correct.
Check whether mini bearings suit your skating
Bont's mini bearing adapter instructions state that mini bearings must not be used for jumping. Choose an appropriate setup for park skating or other skating involving jumps, and ask Bont for advice if the intended use is unclear.
Avoid assuming that a smaller bearing guarantees more speed. This guide helps you establish compatibility; evaluate performance claims against the exact model and use.
Count the parts before ordering
A conventional pair of quad skates uses eight wheels with two bearings per wheel, so plan for 16 bearings. If all 16 mini bearings need adapters, plan for 16 adapters too. Check the selected pack contents and whether any required spacers are included.
For installation and servicing, follow the instructions for your bearing and tools. Read our bearing cleaning guide and use the roller skate bearing guide for broader questions about materials and ratings.
Before buying, write down your axle diameter, wheel bearing-seat size and current bearing code. If any detail is uncertain, contact Bont with the wheel and plate model so the complete combination can be checked.