I've been using a Shure AXS 4 off and on for the last 5 years or so. It was the only condenser mic I had access to, and has been great at recording acoustic guitar and okay on some vocals. I can't find much info about it, though. I noticed that it looks externally identical to the currently manufactured Shure PG81. The PG81 is even represented the same way on the shure page, saying that it has flat frequency response and is ideal for instruments. It's not critical. The mic is what it is, but I've always wanted to just look at the specs on it.