The 9 cm (3.6 inch) [54.3 x 72 mm] measurement refers to the size of the screen protector that is compatible with a specific device. Our website sells a range of screen protectors that are designed to fit various devices, including smartphones, tablets, and laptops. By providing the exact dimensions of the screen protector, customers can ensure that they are purchasing the correct size for their device. This ensures that the screen protector will fit perfectly and provide optimal protection against scratches, cracks, and other types of damage.