This spacer allows you to use the non-Viggen ABS sensor mount with Viggen axles.
The Saab 9-3 Viggen ABS sensor mount is getting harder to find and the non-Viggen bracket will blow apart if you try and use it alone.
The tone-ring on the Viggen axels are larger than the other models and this causes a problem when your mounting bracket breaks and it need to be replaced.