Presence Boost Adapter adds 3 to 5dB of high-end enhancement between 5 and 9kHz, improving clarity of speech and adding definition to instrument sounds.
It is sold together with C1000s mic, but you are going to lose it anyway, so buy an extra one. It is very easy to lose.
Pros: I use it for classical guitar and the presence of sound is really better. You can put it on or off manually, if you pick apart your mic, so there is no extra switch or circuit for it. All in all, simple and usefull.
Cons: Quite stiff when clicking on or off. It goes straight to the top of capsule and this movement has to be a sensitive one. Unfortunatelly, can not be used together with PPC 1000 Polar Pattern Converter at the same time. Probably there is a reason for it.