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 televisions. 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 that are specifically designed to fit this size screen, providing protection against scratches, smudges, and other types of damage.