I purchased this feeder from the local farm store when we bought our days old chicks. We did not buy the jar for it at the time, as the feed store lady said we really wouldn't need it. We found out later that a jar would have helped the poo from getting into the feed, but such is learning through example. The feeder consists of a top part with the feed holes in it, and the bottom part that holds the feed. This separates very easily, so we found we had to really make sure those two pieces were secured before filling. I did come to find out that a regular mayonnaise jar fit the base perfectly (we didn't have a mason jar) so that solved the poopy feed problem. This is great as a starter feeder- we just upgraded to a hanging feeder since the chicks are over 8 weeks old now and this feeder is getting too small for them. I'll still use it to put treats or grit in for when the chicks are adults, but the feeder is really small and probably is better suited for the chick stage. Again, it is a very cheap price so I am not complaining- it held the chick starter food just fine, and with a jar on top, I didn't have the poo problem that we did at first. If you do use a jar, be prepared to see the jar half-empty when you turn it over to fill the feeder- although this didn't bother us so much as we used the jar more for a poop shield anyway.