1/16 is all I need and it works well for 2f and 3f. I tried 5/64" and 3F starts coming out (Graf's, which is a little smaller grain size than Goex), but you could probably go all the way to 3/32" for 2F Goex and it would likely never plug, although you'd be venting some pressure. The smaller holes (under 1/16") worked well with 3F Swiss, but caused problems (fouling) with other powders. I agree with SC Loyalist for 3F -- when the hole gets ~>3/32" it is time for replacement, sometimes before. It will start to shoot a little funny and erosion goes faster and faster -- at least that is what happened to me.