Latex. If you want maximum support, get this, I have one in Firm. It's about 7 inches high!
https://www.amazon.com/dp/B00WJ0AGH6/ref=twister_B00WJ0ADJC?_encoding=UTF8&psc=1
I also have a medium Talatech that is nice, about 6 inches high, good support, but a bit more give than the Brooklynn...