the atomizer, needle and even slide come in many different sizes and types for the bings.
the atomizers are numbered in mm for the opening that the needle goes through i.e. 2.12a, 2.15, 2.17, 2.20, 2.22, and 2.26 the 2.12a has a recessed hole, since it wouldn't accomodate a needle at full top at that size.
the needles are marked by rings and clip positions.
the slides are too many for me to remember. some of them have holes drilled from the front down to the needle, some have bigger or smaller air channels on the bottom of the slide, some have no channel at all.
but back on topic:
what are you looking for? a cross reference between drill sizes and jet sizes?