I have a Robbins top.
ROBBINS AUTO TOP COMPANY | CONVERTIBLE TOPS
I'm not sure if you'll be able to dig around in here and find that info, but the Boxster tops are all the way at the end.
If I had to venture a guess I would say it is Twillfast like what is seen in Autotopsdirect's website. I know mine is not an A5 acoustic version, but I will still say that even at a lesser cost it's a great quality top and it holds up to the weather (rain so far, at least) beautifully.
What they mention in those notes about the top coming out of the channels when opening/closing, that does happen, and still did happen once or twice with my new top. It's simply a known problem with Porsche, and I've just gotten in the habit of checking it, as it always happened on the driver's side. I will say also that the Robbins site is the first time I've seen anything that mentions that there are updated parts that can fix this.