Thank you for reaching out with your question. For a cockatiel we would recommend the Medium size Multi-Branch perch. If you have any further questions, please reach out. Thank you!

I got the small for my budgies and they love it.

The small branch is great for budgies.

Since this is a natural product it's a bit of a toss-up what you're going to get. I've purchased 6 or 7 of the large and x large for our macaws. I've been mostly happy with them, there was only 1 that had a much thinner cross branch that one of our birds quickly chewed off. I was looking for thick wood and not a lot of crossing branches and the bigger sizes did that for me. The overall length that they spec is pretty accurate and the larger sizes tend to have thicker branches

Thank you for your online question. The hardware does not contain lead or zinc.

The small is only about 1/2" diameter - great for my parakeets but I would get the next larger size for a comfortable fit for a conure's feet.

Thank you for your inquiry. We would recommend the medium size for a Timneh African Grey based upon size.

The perch has a butterfly screw with a couple washers, to be screwed on tight in between cage bars. I am wondering, though, if these might be too wide for finches? I bought the small size and it is right for my conures, though I still feel my smaller green cheeks need an additional thinner perch (about pinky finger width). But I don't know about finches...they might do well even on wider perches, I think they probably have the same type of feet as a songbird....whereas the parrots are zygodactyl, and I think perhaps they are more dependent on gripping on perches? Not sure. Anyhow I'd still suggest a variety of sizes of perches for all birds :)

I purchased the medium 32 inch for my cockatiel. It is perfect!