FYI....I made one...badly but it works. I keep a funnel hanging in the coop to put in the top so I can put the feed in and it not go everywhere.
I am going to make another like the video for my oyster shell.....I like that it is not as big around as mine that I put feed in. I think I used 4" or 5" pvc. Well, I thought I knew what I was doing. My DH came in from out of town working and told me everything I did wrong. My joint at the bottom is the wrong angle so sometimes I have to poke the feed down. But I am looking for the right angle.
But, the funnel really helps in loading the feed.