For Stoptech BBK, minimum size spacers for the front is 15mm. You can step up to 20mm or 25mm if you want. If you use 15-20mm, you will need to change out your oem lugs for extended ones. For 25mm, they have built in studs manufactured by H&R or other off brand. For the Rear, go with a 25mm to make it flush with the fronts.