The 43.4 cm (17.1 Inch) [378 x 212.8 mm] measurement is the screen size of a specific device that our website sells a range of screen protectors for. It is important for customers to know the exact size of their device's screen in order to choose the correct screen protector that will fit perfectly and provide the best protection. Our website offers a variety of screen protectors that are specifically designed to fit this particular device, ensuring that customers can find the perfect match for their needs.