I ordered my regular size - I am tall - and the tights barely fit me.  Also, they are NOT opaque.  They are very dark and are much heavier than panty hose, but they do not block out the skin completely.

They look good and hold up to use, but they are not opaque so that's why I marked them down.  Also, I'd suggest you go up a size.  C/D is usually perfect for me (I am 5'8" 135#) but they were on the short side and the panty was TIGHT.