These are awesome. They're 1/4" thick, exceptionally lightweight, and seem, by all accounts, to be removed of ABS plastic or something comparable. I can flex them somewhat when I twist them the long way, most likely on the grounds that the sides are so tight along that length. Regardless I think they'll give a strong, stable surface to mount speakers to once they're strengthened from behind by the auto entryway. The CNC tabs are still on mine, and the gaps are just penetrated through on one side on one of them, so I'm giving four stars generally speaking because of the fit and complete as opposed to five. Visit http://soundexperts.org/