Respectfully, I would recommend no happy huts. Here's why, from a very scary experience:
The traditional polyester kind (usually green or blue and fuzzy) are the most dangerous because they fray easily. There are also fleece ones (typically more triangle shaped) that don't have as fluffy of material, which are safer but still dangerous. Cotton is the safest material you can use, but that still has dangers of snagging nails, choking, etc. Our beloved GCC got terribly sick (and many, many others if you research have DIED from these) and we took her to the ER vet. They found strands from her happy hut in her vomit (and yes, it was vomit not regurgitation). My vet was very angry that I had one but I didn't know otherwise! I thought she was crazy and mean but she told me about some of the ways she has seen birds die from these. My girl never EVER not once chewed her hut *that I saw*. So even if we don't think we see it, they could still be ingesting small particles, or even making a ware mark in the fabric to become entangled and die or get severely injured. Ours had no ware marks and still looked new. And they can ingest small particles over time and it just sits there building up in their crop and they seem fine until one day it causes crop impaction. On top of those dangers that countless birds have died from, they also can cause hormonal issues such as aggression and a bird becoming egg bound which is critical and often fatal. Very scary. And in both situations, the smaller species are basically not able to be operated on simply due to their size. This is all per my Avian Vet.
I am now a forever customer of Critters Choice Small Animal Chube. All of our birds have them and I order multi-packs on Amazon and they are durable, safe, fun for the birds, and built to be chewed so no worries! I know of a lady who contacted the manufacturer and discussed the product, materials, and manufacturing process, and she is confident in these. They are becoming a huge hit in the bird world. Some people even hang little toys inside. Our birds took a little while to get used to them, but now they love them and nibble the edges, and sometimes sleep or hide in them. The Chube is also not fuzzy so it's less resembling of a nest (which helps prevent hormonal issues I mentioned above).
I am humbly and respectfully very passionate about this topic, because I don't want any other birds to suffer, or their guardians to experience the grief that I did when I almost lost my baby. They have great alternatives out there like Chubes, natural seagrass huts, Jolly Balls, or even plain food grade cardboard boxes. We all just want the best for our babies, but please please consider what I'm sharing with you - and maybe research on Google about the sad, but true, things that have happened with those huts. I just wish manufacturers would make safer huts - at lease ones made of 100% cotton which would be a little safer...