I quickly checked online and found a really good brochure from YLI that gives lots of info on thread. I especially like pages 8-9 that explains the new number system, called TEX, and gives a great chart that compares brands, each with their old cotton count or denier number with the new TEX number. You can find it at
http://www.ylicorp.com/pdf/tot-brochure.pdf. Might not want to read the entire thing online, but it's the kind of reading I'd print and haul to the doctor's office to read while waiting. I figure when I'm bored, any kind of reading will do!