THIS IS A 3/8" ROTARY CUTTER, Blaircutters provide fast, accurate holes in materials up to 3/6" thick. Blaircutters are annular cutting tools that cut around the edge of the hole & eject the center as a slug. Because they are hollow, there's no dead zone as with twist drills. Unlike hole saws that rip & tear through material, they quickly give you a quality, burr-head hole. Available in seven sizes for 1/4" & larger drill chucks. Spring loaded pilot "pops" the slug from the cutter. 3/pkg.