MK Morse AVPLU01 Plumbers Combination Hole Saw Kit 13 Bi-Metal Hole Saws (AV) And 9 Carbide Grit Hole Saws (ATCG) Arbors Included In Kit Bi-metal hole saws have smooth cutting action with minimum vibration Carbide grit hole saws have a gulleted, snag resistant edge perfect for thin materials Arbors: (1) 1/4" hex, 1/2-20 thread with 3-1/16" pilot drill and (1) 7/16" hex with 5/8-18 thread size with 4-5/16" pilot drill included with kit Extra pilot drills included with kit