Item Specific Drop Chances

I've seen charts of item type drop percentages, but I can't remember seeing anything on this particular topic.

Say a certain monster has a 3% chance of dropping a ring. Okay, say he drops a ring. Your MF gives it a 22% chance to be unique. Okay, so it's a unique. Where are the percentages of what unique ring it will be? Why do so many lower end unique rings drop before say... SoJs? Are the chances ranked on their req'd level?

its somewhere on arreats i remember reading about that too

my chart said that in nrmal there was certain uniques that drop like 5 diff normal uniques each with 20%, then nightmare uniques with 10% each, hell uniques with 5%

thats what my chart said anyway