I purchased both the black and the premium dark in size 7. I am 5'8" and 125 lbs with no real
curves to speak of.
The black pair is 75% cotton, 24% nylon, and 1% elastane - they still fit great,
but have very little stretch and really hold me in.  The premium dark are more comfortable,
with 98% cotton and 2% elastane.
Both pairs are the right length and really flatter my figure!  I will buy more.