The most popular CraftID right now is a 1" round version.  That's because they are the least expensive, get the job done, and are easily embedded in woodwork using a standard 1" Forstner bit.

If you need more space, have larger crafts or artwork, or just need to make a statement then a 1.5" CraftID is really impressive.  It provides plenty of space.  It can be as simple as a signature or logo or can be loaded with contact details and other marketing and inventory information.  Master CraftIDs are only available in 1.5" and larger sizes.  That's because their QR Code message just typically will not be recognized in a 1" size with most mobile phones.

For really large pieces or for customer-facing marketing a 2" CraftID is an excellent choice.  You might use a smaller CraftID as your signature and then use a 2" CraftID in a decorative sign that connects potential customers right to you and your website.