1" body 90° countersink, 3 flutes.
A countersink cuts the tapered seat that lets a flat-head screw finish flush with the surface. This one has a 1" cutting body on a 3/4" shank, 2-3/4" overall, ground to a 90° included angle.
90° is the standard included angle for metric flat-head screws, and the common choice for chamfering a hole before tapping.
