This is a code that Miyazaki uses to identify the shaft stiffness in 4 zones of the shaft from the butt end to the tip end. You can see it explained at this link on their web site.
They use a scale from 0 to 9 with 9 being the stiffest. 7 is the butt stiffness reading, 5 is the mid butt stiffness reading and the first one is the mid tip stiffness reading and the last 1 is the tip stiffness reading on this scale.
Date published: 2014-09-29