Nothing exotic here: just twist bits in steel cutters sized for #4–12 screws. In our tests, every piece in the set cut clean countersinks and 3/8" or 1/2" counterbores in quick fashion.…
As a nice touch, the manufacturer stamps the countersinks with the size of the matching bit. The ¼" hex shanks make for quick in-and-out connection in any hex-chuck drill/driver.
Ease of Use
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