Anyone try the cheap Chronographs from Ebay and Amazon?

Anyone know about this one? Aliexpress

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I'm new to the whole PCP game. I got one but the only thing I'm using it for is to dial in my hammer spring to find the best FPS for one of three pellets I use. I also validated this cheaply Chrono against two others that considerably more expensive and mine was with in one or two FPS. What else can I use this for.
Anything that flies🥴