The 48.3 cm (19 inch) [410.9 x 257 mm] measurement refers to the size of the screen that our website sells screen protectors for. This size is commonly found in desktop computer monitors and some all-in-one computers. By providing this information, customers can ensure that they are purchasing the correct size screen protector for their device. Our website offers a range of screen protectors designed to fit this size screen, providing protection from scratches, smudges, and other types of damage.