I got this for tuning acoustic instruments.
It's cheap and in theory it's a useful product to have in a studio. Unfortunately the cable is far too short for any permanent connection so you'll need to re-attach it every time you need tuning.
Build quality is almost unbelievably poor. It's so fragile that I was actually worried every time someone used it. I packed it carefully away each time to avoid breaking it. Too much hassle for something that WILL break, sooner rather than later. I know it may seem a bit harsh to criticize build quality when it hasn't actuall broken yet but trust me, this is as cheap and fragile as it gets. Any more fragile than this and it would have fallen apart before you even open the box.
There are better ways to tune an acoustic instrument. Simply using the "clamp a pair of headphones around the guitar"-trick and plug it into a tuner works just as good. Or use a tuner with a built in mic instead. Or simply tune by ear, which is often both faster and better.
It may seem like a useful product but it's actually not that great and soon turns out to be redundant, especially if you already own a tuner with a mic (and if you don't you probably won't need this one either!).
I still keep it around, carefully packed and stored in a drawer for those extremely rare situation when someone needs tuning an acoustic instrument where the headphone-trick can't be used due to physical limitations and tuning by mic or ear for some reason isn't ideal (like lots of background noise).
I guess it fills a VERY small niche in my studio but it's not something I really NEED and I wish the build quality could have been just a little bit better and the cable a bit longer. Then it could have been a more useful tool.
Finally, in case anyone wonders: No it's not suitable for recording. It's not meant for this and the sound quality is awful. Maybe for triggering something... but still far too fragile to be trusted except for very occasional CAREFUL use.