Xiaomi debuted its next-gen Mix Fold 4, which is 9.47mm when folded close, making it one of the thinnest book-style foldable phones sold commercially -- second only to the Honor Magic V3. The Mix Fold 4 has a 6.56-inch outer screen that opens up like a book to reveal a 7.98-inch inner screen. Both screens have a refresh rate of up to 120Hz.

Xiaomi credits the Mix Fold 4's "all-carbon architecture" for reducing its weight and thickness. It also reduced the hinge's total volume. According to the company, the hinge floating plate, screen backing plate and middle plate battery compartment are all precision-molded from carbon-fiber materials. Carbon fiber is a strong and lightweight material, but it comes at a cost and has been reported to suffer from brittleness.

Despite the thinner design, it's expanded the Mix Fold 4's battery capacity by 260 mAh, bringing the total capacity to 5,100 mAh.

BM2H and BM2G for Xiaomi Mix Fold 4.

The Xiaomi Mix Fold 4 has four cameras, consisting of a 50-megapixel main camera, a   50-megapixel floating telephoto lens, a12-megapixel wide-angle camera and a second periscope-style telephoto lens.

Xiaomi says the Mix Fold 4 has been tested to withstand 500,000 folds. It has an IPX8 for water resistance, which means it can survive submersion in water, but it cannot protect against dust ingress.