What the concept of Ultra-thin mechanical watches?

Ultra-thin mechanical hand was classified as one of six technologies .
What is the concept of ultra-thin in the end? What is thin? What are the specific parameters of the standard?

Handscroll less than 2 millimeters, automatic less than 2.5 millimeters, and are considered ultra-thin, ultra-thin is not good to do, one is a rugged challenge, one of the challenges of structural design, then one is on the processing technology challenges.

I tried a number of ultra-thin parts, more than paper thin, than the m small, on the table, with his nose in the air can be blown dynamic. Unfortunately, now Chanel j12 watches popular Heavy, thin it a little useless.
History there is well-known ultra-thin Chanel watches, Swiss watches and so on.