It sucks, I fried 2 that I tried to use on my racing pocketbike. They are too sensitive on the input lead, too much signal and they lock up and die.
They have a warranty, but the company that sells them (not the ebay guy, but the distributer himself) seems like some guy in a garage. It took a couple months to get my replacement. I called several times and got the run-around from the guy. Had to keep reminding him and always got some cock and bull excuses.
Get the Sendec Tach, for a chinese piece (and what isn't these days) it works really well for me.