I've been to 3 different CCI classes, plus two of my men attended a class and it is constantly referred to. For every casting we still use our CCI concrete calculator (it's what my guys ask for when we have something to make and I email it to them on their phones). Plus Jeff is always available to help with new problems that come up. Conditions are not always the same, and who has time to experiment, so we ask Jeff and he guides us in safely and effectively.