These single flute countersinks produce ultra smooth, round countersunk holes in a wide variety of materials. The single cutting edge will cut faster than standard multi-flute countersinks and leave a finished hole every time. They can be used in hand drill and drill presses. They can be resharpened. Single cutting edge prevents chatter and produces smooth drilling action. This set includes four of the most popular sizes: .267, .298,.343 and .391. Shank sizes are 1/4 inch and will fit in any 1/4 or 3/8 inch. Cut angle is 82 degrees. Comes in wood store box.