I’ve never heard of this program - which is odd if it is so effective. I am rather suspicious of its claims as (from what I can see) it doesn’t have any published studies in research journals. It bases its claims on a book written by the guy who came up with it: “HCRI fluency outcomes are demonstrated in a large scale evaluation study, which is documented in Chapter 11 of the book, From Stuttering to Fluent Speech, 6,300 Cases Later: Unlocking Muscle Mischief, written by HCRI President and Founder Ronald L. Webster, Ph.D.” There are evidence-based programmes for stuttering out there but, personally, I’d be a little wary of this one unless they can prove their claims.