Bought a few of these at the same time, and for me, none of them were still working after a couple of weeks.
Gave most of them to a friend of mine and he seems to be using them away. No idea why this is, because there's nothing wrong with my (multiple!) instruments.
So, bizzarely, they may work for you, they may not. I suppose they're cheap enough to give it a shot if you want, but I personally would not want to be relying on them.