v28Long Leg Warmer, Womens Men 80s Party Ribbed Knit Dance Sports

Q: How do they stay up? Is there an adjustable tie, or elastic or.. what?

They do not stay up very well on bare legs. Do fine with tights though. There is a tie that you can tie tighter but that does not make them stay up any better for just bare legs.

Q: what is the material?

Made of 80% Viscose & 20% Nylon

Q: How do we select the length because I'd like the 32"

Those will go up to your thighs

Q: Do the neon colors glow under black lights?

I did not order the neon colourway but I looked at the description carefully and there is no mention of them being light reactive. If this were a feature it seems likely they would promote it to further sales. I also looked through reviews posted and there were several people with them in neon but I didn't see anyone talking about that as a feature of the product. You might reach out to the manufacturer directly with the inquiry. I'm sorry I couldn't answer more fully.