What size screw extractor to use on caliper guide bolt?

To remove a caliper guide bolt, it's typically recommended to use a screw extractor that is slightly smaller than the diameter of the bolt. Common sizes for caliper guide bolts are M8 or M10, so a screw extractor in the range of 6-8 mm or 8-10 mm would generally work well. Always ensure the extractor is appropriate for the thread type and condition of the bolt. If unsure, consult a repair manual or seek professional advice for the specific vehicle.