High carbon steel; heat treated for longer life. 4 flutes for clean, accurate boring. Designed for use in all woods. Countersink can be mounted on taper point, brad point, and regular point drills. 3/8" diameter; fits #5 screw bit.
Having used several different countersinks at work over the years I really like this one. It works great, has 4 cutting sides and most importantly it can be resharpened many times with careful attention to the angle. Works great and means a lot to me. It has two small hex screws on each side to tighten it onto the bit.
Pros
Countersink can be fitted to cone point, abrasive point and regular point drill bits