Review on HHIP 2007 0021: Advanced Interchangeable Counterbore Set for Precision Machining by Elvis Kimbro

the quality here is doubtful. I don't see any markings, but I suspect they were made in a densely populated country in the Far East. I had to drill out the bit holder to fit the individual bits. They were a few thousandths too small and they didn't fit. In addition, the fit between the guide shafts and cutting tools is imprecise and can allow for eccentric holes. I haven't tried them on any significant quality materials like steel, but I'm not optimistic. I would look at auctions for a set of used American made pilot bits.