I have noticed a few questions on this forum asking about switchable-glass technologies like liquid-crystal and electrochromic. A new switchable-glass technology was commercialized this year. It is called suspended-particle-device (SPD) technology. SPD glass allows you to vary the light transmission of glass or plastic from almost clear to almost dark, and everything in between. Like competing technologies, SPD film or glass requires a voltage to control the light transmission. In my opinion, it is far superior to liquid-crystal and electrochromic technologies because it responds quickly, lasts longer, is more temperature stable, has no IRIS effect, is less expensive, and works with flat or curved surfaces.
SPD film and SPD glass is commercially available in the following transmission ranges are
2 to 30 percent
5 to 50 percent
10 to 60 percent
If you are interested in SPD switchable glass, here are two links for more information: