Your looking at a Brand New (5) five piece set of countersink bits.

This type of bit is specially designed to be used after you drill the primary hole you need for a screw or fastener, you use this type of bit to produce a tapered edge around the primary hole in a larger diameter to allow for the head of a screw or fastener to sit flush with the top of the work piece when tightened down.

These are frequently used on woodworking applications where the head of the screw must be flush with the surface of the work piece, this is also frequently used in machine shop applications in metal plates.

This set includes sizes:

1/4" , 3/8", 1/2", 5/8", and 3/4" diameter bits.

Specifications:

These bits are made from high grade carbon steel that has been heat-treated and coated in Titanium which helps dissipate heat to keep the bits cool while cutting which helps creates a clean, smooth cut and the cutting edge will stay sharp and retain it's profile 7 to 10 times longer than a standard un-coated but will.

Each bit has a 1/4" diameter shank so they can be used in any type of rotary tool from a cordless drill, to a drill press.