Perfect for the right situation
I've used these for years. They are tough and they do the job. Those who may be new to impedance transformers, note that in many situations it is better to buy a box that also has a ground lift switch (such as the IMP 2), as the ground lift can remove noise issues caused if your setup has a ground loop. The IMP 2 (and similar products) also includes a pass-through for when you want to run both high and low impedance from the same source.
Note that both the IMP and IMP 2 are passive (not requiring a battery), which means that they do not have a control for compensating for volume.
Again, the IMP is great for the right situation - it is solid, works perfectly and is inexpensive.
One more note: There is a user comment from some years ago about the IMP affecting the volume. This is not a simple adapter, but an impedance transformer. If you're not sure what you need, talk to a sales tech at Sweetwater.