High-speed steel 7 piece 90 degree 6 flute countersink set. HSS sets include one piece each of 1/4", 5/16", 3/8", 1/2", 5/8", 3/4", 1" body diameter with a particular included point angle. High-speed steel tools are good for most general purpose applications, offering a combination of hardness and toughness for wear resistance. Uncoated tools feature just the base substrate without any additional treatment or coatings and are suitable for a wide range of applications. 90 degree angle.