I bought 2 of these from Amazon for about 10 bucks a pop. the first one would work for about one week (no return) and the second one did indicate something but that was far from the real RPM. I guesstimate it showed 4000 when the engine was doing 2000 but even that is useless as the indicator jumps from 3000 to 4000 up and down permanently - this is probably what one can expect for the price but nevertheless - I would rather spend the 100-plus Euros for a real instrument (have one on order from Germany)
