2mm and made out of durable plastic, styrene is an excellent alternative to traditional cardboard mounts. Fiber-based mounting substrates tend to absorb water over time, which leads to bowing or warping. Styrene has no natural fibers, and therefore is not affected by changes in humidity. This means no more warping! As an added bonus, it’s more resistant to edge and corner damage than cardboard mounts, too. Only available in white.