My .30-06 dies arrived today. Older style, not headed pins. Thanks for the part numbers!Not at all a stupid question. Your answer is, it depends.
You'll need LARGE decap pins in older model RCBS dies. They are typically sold in a bag of 5 replacement pins. RCBS Part number is RC09609.
If you have a set of new production '06 dies that you just purchased from a supply house, those are using headed pins. Part number on those is RC90164.
When in doubt, with sizer die in hand, best bet is quick disassembly. A visual inspection of the pin will confirm the pin type.
A headed pins looks like a pin with a nail head on top of it. The old model pins are straight.
Edit: Should have mentioned also, if your RCBS dies are using headed pins, there are no large and small sizes, so don't bother hunting. RCBS Headed pins are one size fits all.