I bought this for tail blades on a 450-500 but they don't work too well. Tried it on a 250, not so good there either. Problem is, the carbon is thin and there's no spring so it doesn't want to stay in place. And it doesn't want to stay vertical. Readings were inaccurate and couldn't get the same reading twice. Looks great, came in a nice case (didn't buy it here tho so not sure how it will arrive). But the e-flite micro plastic gauge is working better for me.