Ron, as far as I'm concerned, any gauge like these is just to get you close for the trial cut. I'm not sure I'd trust a digital gauge any better, at least not at first. That's if you really need to be that accurate. In many cases, the rough measurement with these would be good enough. The price plus shipping is about the price of as fast food meal deal but this one will stick with you longer so if you use it much at all will be a good deal.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.