The 43.9 cm (17.3 inch) [383 x 215 mm] measurement refers to the size of the screen that our website sells screen protectors for. This size is commonly found in laptops and notebooks, and our range of screen protectors are designed to fit this specific size perfectly. By providing this information, customers can ensure they are purchasing the correct size screen protector for their device, which will provide optimal protection against scratches, smudges, and other types of damage.