Sorry long post but I promise it's worth the reading -
I forgot to mention the Kaytee Chewbular comes with pet bedding (like for guinea pigs) and it's dangerous for birds so that part must be thrown out of it. And I confirmed with Drs F&S that the cardboard binding agent is lead and zinc free and parrot safe
If using a happy hut, it's best to not use the super fluffy kind and get the ones that are more tight-woven material. But all of them are still dangerous for ingesting and snagging nails. There are woven seagrass huts too but I have never trusted them and I actually heard about a bird that broke a leg from getting stuck on one of those.
We almost lost our GCC (who is my BABY) likely due to her happy hut. The vet found fibers from it in her vomit and got upset with me for having one. I didn't know! I thought she was a bitter old lady with no feelings for even suggesting not to have one! Well I did a lot of research online and there are countless stories of birds dying from them. Even birds that had one for years and never chewed them and one day they did and it killed them. In the garbage it went! My girl slept on a perch for a couple months and I felt SO awful but finally got comfortable with her chew tunnel and now she LOVES it! And dual purpose she can chew the edges and it's fun for her! I drill holes in mine and hang with vegetable tanned leather from the top of the cage.
BTW, I never ever saw my girl chewing hers, ever! It floors me that they are even legal to manufacture and sell knowing what I know now. I'm so thankful I found out about this. Here's a quick sum of what I've researched and/or experienced personally:
Happy huts:
-choking hazard
-crop impaction hazard (which, if it doesn't kill a bird right away it cannot be operated on smaller birds per my avian vet, and it could build up over years in tiny ingested amounts and one day cause illness or internal infection)
-toe snagging hazard (which can cause birds to die from exhaustion trying to get free, or chew off their toe or leg, or break wings trying to get free, or fall upside down and the blood rushes to their head and that kills them).
-contribute to hormonal behavior (biting, excessive cage territorialism, egg-laying which can be fatal and should not be encouraged).
Chewbular tunnels:
-provide a hideaway and sleeping area
-safe to chew (zinc and lead free)
-very durable
-entertaining for birds
-very affordable and easy to replace when needed
-no danger of feet or beaks getting stuck
-no choking or strangulation danger
-isn't fluffy and therefore doesn't resemble a nest as much (to contribute to hormonal behaviors mentioned)
-resembles more of a natural hideaway that birds would sleep in in the wild (tree trunk holes)
Trust me, it feels REALLY BAD to get rid of them, but your birds will get used to a new tunnel. You can have it out around the house for a while to get them used to it and gradually put it in their cage right where the hut was and put treats in it for positive association at first. Give it time and they will learn to LOVE it!!!

I honestly found it hard to believe that a toenail could get stuck and kill a bird, until I saw a picture of a little GCC hanging upside down just from ONE toenail snagging her hut, and she had passed away from it (either exhaustion or blood rushing to her head). When birds catch their toe on something, even a shirt or hair, they FREAK and panic immediately, hence broken legs and wings when it happens with "happy" huts. That was what pushed me over the edge.