I, Sebastian Zetin, of Zetin Audio, guarantee all of the parts within the Z87 microphone, with the following exceptions (I built the mics, so I know how to troubleshoot them, should anything arise):
1. You blow into the capsule or otherwise damage it. The capsule is the most expensive component of the mic and is built in a vacuum sealed device in a lab somewhere, so I can't just go around replacing these. But the ONLY times I have heard of a capsule needing replacement was on a fifty year old mic, because someone dropped it, or because someone blew directly into the capsule (DO NOT BLOW DIRECTLY INTO THE CAPSULE). I can replace the capsule, but it is at your expense. They run around $150, plus labor. So take good care of the capsule and it will last a long, long time.
2. If you drop it or do something else to damage it, I can attempt repairs (at a fee), but my guarantee is for the BUILD of the mic, it is up to you to take care of it.
Aside from that, I guarantee all of the parts to work properly from the get-go. And the parts are all of the highest quality and, as such, are VERY unlikely to become faulty. But if one does (or if more than one, by some rare misfortune), I guarantee I will repair it. And not only that, I will give you a loaner mic to use in the meantime, that will be a perfect match (I am meticulous about making them all match perfectly) so if you have a deadline coming up, I am basically guaranteeing a zero-downtime kind of deal, which I hope makes you happy.
I am very strict about quality control, so you will be buying a mic that has been thoroughly tested and passed a rigorous inspection.
-Sebastian Zetin-Zetin Audio