Chinese startup Xteink has unveiled the X4 Pro, an ultra-compact e-reader slightly larger than a credit card and designed to attach to the back of a smartphone. The device is 5.95 mm thick and weighs 72 grams. It has a 4.3-inch touchscreen, page-turn buttons, a front light and 16GB storage expandable to 256GB. It supports only non-DRM epub and mobi files and is priced at $99.

Design changes are accelerating in the electronics market as the European Union prepares to implement new battery rules requiring users to replace batteries themselves. The shift is emerging first in peripherals such as headphones, e-readers and handheld game devices, rather than smartphones. From Feb. 18, 2027, many portable devices with batteries must be designed for user removal and replacement, with makers also required to sell compatible batteries for at least five years.