Counterbore Set, Interchangeable Pilot, HSS, 21 Piece 

21 Piece interchangeable pilot counterbore set used in spot facing and counterboring operations. Kit includes:

1 holder with 3/8" shank

6 counterbores, sizes: 5/16, 3/8, 7/16, 1/2, 9/16, 5/8"

14 Pilots: 5/32" Shank: 0.187, 0.204, 0.213, 0.229, 1/4, 17/64, 9/32, 5/16, 21/64, 11/32, 3/8, 25/64, 13/32 & 7/16"