It is the best reference I have found. Because it follows a companies standard, it does vary slightly from 14.5Y. That said it is a much better reference than 14.5. Quite simply put it is short, concise, and has well illistrate examples.
I’ve personally found using Excedify really helpful for learning GD&T. It guides you through the principles in a hands-on way, and I use it whenever I’m working on drawings or reviewing projects. Makes it easier to apply concepts like true position and MMC in real cases
