The Phillips Pin Head Bit is designed to drive a particular size screw. Each bit is 'size-specific'. The #1 Bit will fit screws up to #6 diameter which are no longer than 1" in length, the #2 Bit will fit screws from #6 diameter which are longer than 1" in length through #10 diameter, and the #3 Bit will fit #12 and #14 diameter screws.
