Our 1/4" Round Arbor fits hole saw sizes 9/16 to 1-1/8, and includes one 1/4" diameter high speed steel hole saw pilot drill, and our 7/16" Hex Arbor fits hole saw sizes 1-1/4 to 6", is a 'quick-change'arbor, and also includes one 1/4" diameter high speed steel hole saw pilot drill.