I was rebuilding and working on so many different types and brands of engines several years ago that I finally had to break down and buy a good tach. I had both the Hobbico and GloBee and neither of them were accurate enough, I finally bit the bullet and bought the TNC tach, it's perfect and accurate but at $100.00 I question the need for most sport pilots. I compared it to other tachs every chance I had and one thing became clear to me, there was/is a combo tach sold through Horizon that is a combo volt meter tach and everyone I checked against mine was spot on. I do use my tack to tune the older type of YS engines because they are a balancing act to get the high and low ends adjusted and I can't hear the rpms when I get the sweet spot. I need it to tune a couple of gas engines I have too but I can still get away without one. Everyone needs a good volt meter though and that combo tach and meter from Horizon is a much better idea then just a tach. TNC makes a great tach though but is it worth $100.00??? It was at the time but doesn't get used all that much these days.