you leave water in the bong, the ashcatcher can do one of two things - if you put water in your ash catcher, it acts as an extra filter for the smoke to pass through, if you leave it dry it is for the soul purpose so that your bong stays clean. though it will also help keep the bong clean with or without water.
if you scroll up a 4-5 boxes from the bottom, both the ashcatchers you pictured are there.. They sent you ASH1 instead of ASH5.. both are the same price though (btw, gorilla glass is a wholesale distributer, so minimum order is $150 or 12 items.)