It measures out to about 1/32" or maybe .75mm or so. T-visors' one that I got is like yours, 3mm or 1/8" acrylic. I tried the T-visor one and at night found it very hard to see what I was doing. Maybe wearing glasses makes it worse. I made this version so I could see at night like when I trooped at the Episode 7 premier. I'm looking for a lighter acrylic but there seems to only be one darkness available.
Here's a comparison shot:
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No, it's not screen-accurate but I think it does well enough, I'm more comfortable being able to see where I'm going. Since I discarded the packaging, here's a link to what I used: 16" x 20" Polystyrene and Backing Kit by Studio Decor® It's enough to make at least 3 visors.
And here's the window tint film I used:
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