I ordered the white with black polka dots and these are the nicest sheets I have ever owned.  They are definitely 600 thread count like advertised and the packaging also says they are 600TC.  Perhaps in another colour the TC is different.  I wanted to order a king-size duvet cover in the opposite colours (black with white), but the sizing says the king is actually a king/California king which is about 10" longer and 8" wider than an actual king.  I would definitely order the sheets again.