ok I use two of these, because they were so cheap. It looks complete to me, besides the little grill thingy that goes over the pump, but thats not 100% necissary. I personally cover the bottom of the filter with filter floss (polyester pillow stuffing) so that it catches debris, and then I fill the entire inside with the ceramic bio media pieces, or you could use lava rock. I will change the polyester fiber when it needs it and once a month rinse the ceramic bio media in used tank water to get rid of any debris that get caught. I highly reccomend this way, because the little spongy piece thats supposed to go in the filter and let bacteria grow is so small I dont see how it could really work.
Good luck!