Gear with holes/slots

I have found a chest piece with what look like 4 green holes/slots in it.

What goes into these holes/slots i presume it is to upgrade them but what do you use and where to obtain if this is so?

These are slots for Materia.
This guide should answer all your questions http://www.ffxivinfo.com/materia/guide.php

Quote:

---

Originally Posted by HinaCake

These are slots for Materia.
This guide should answer all your questions http://www.ffxivinfo.com/materia/guide.php

---

awesome thanks for the link..