The 54.1 cm (21.3 inch) [433 x 325 mm] refers to the size of the screen that our website sells screen protectors for. This measurement is important because it ensures that customers can find the right size screen protector for their device. By providing this information on our website, customers can easily identify the correct product and protect their device from scratches, cracks, and other damage. Our range of screen protectors is designed to fit this specific size, providing a perfect fit and maximum protection for the device.