As per my research, they are Polyamide lenses. Reviews on Aliexpress are very good.
Video at https://www.youtube.com/watch?v=d2nzNkqRfNU
Xiaomi Mijia TS UV400 Polarized Sunglasses
Self-repairing coating, 6-layer polarizing films, Z shaped glasses temple and UV400 protection. Experience extreme comfort and durability without renouncing the stylish design of your sunglasses with the new Xiaomi Mijia Polarized Sunglasses.
In recent years, our bodies increasingly suffer from the destruction of the ozone layer, which prevents the excessive penetration of solar UV to the Earth. Large doses of ultraviolet radiation increase the risk of eye diseases. This UV400 Polarized Sunglasses can block ultraviolet rays and protect your eyes.
The Xiaomi Mijia TS Sunglasses have been designed with a technological DNA called chromance, this combines the benefits of polarised filtering with a striking colour enhancement to suit your needs.
Features
With self-repairing coating on the spectacle lens, it will aromatically repair itself under ultraviolet radiation while the lens are slighted scratched within 20um depth, making the lens lasting and new.
6-layer polarizing films can effectively cut down the strong light and eliminate the dazzling reflect light and scattered light, bring you a clear visual effect.
Z shaped glasses temple makes the glasses suitable for different face shape and width, self-adjusting design makes it comfortable to wear.
The clamping force of the sunglasses is only 0.25N, can effectively reduce the pressure on head, free to wear.
Adopting flat glasses lens, reduces dizziness and make you look more clear.
Comfortable TPR nose pad and silicone temple cover are skin-friendly, perfectly suitable for wearing.
What!! You mean the coating repairs itself? Of do i have to repair damaged coating myself?