Review on Precision Circuit and Jewelry Engraving Tool: Genmitsu 0.1mm to 3.0mm by Seth Singh

Yes, these bits are brittle. You have to keep in mind that they are used for slight wobble or misalignment in the jig and they won't lock in place Dremel. say they are a lot stronger than most and can work on a drill press or dremel tool it's just have new bearings and a steady hand or they'll even break.