Our older grill cloth from the VR-4 Gen 1 was selected for best sonic transparency versus "black-out" cosmetic appearance. When "beta" testing a thinner cloth that allowed the inside of the speaker to show, we had complaints from house wives who didn't want to see the internal components of the upper M/T unit.
For this reason, back then we selected a cloth that was difficult to see through, but still enabled the tweeter to get to 25kHz without more than 0,5dB attenuation.
Today, we offer replacement "socks" made from much thinner fabric that you "can" see through, if you have the speakers in front of a window, for those customers who aren't worried about visible internal components. The new socks cost $200/set of four.