Go with the B, I was worried it was going to be too big and heavy, but it's not, it's really awesome. I have a 7 - 7.5 inch wrist,, the 13 link, which is between 17cm and 18cm fits great.

The Self Edge x Iron Heart 19oz Denim CPO Shirt - SEXIH25-CPOOD - Overdyed released today is spectacular.