.090 is pretty thick actually, it would be about 3/32" or right between a sixteenth of an inch and an eighth of an inch.
I haven't used them yet but have been eying the Egyptian ones from the same site:
A EGYPT WALLS-ISIS AND NEPTHYS ON TOP OR BOTTOM
Also ABS is not the stuff they make the cheap masks out of. See this link for an ABS description:
Parma Plast as, material descriptions