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, and this particular size is intended for a specific model. By providing this information, customers can ensure that they are purchasing the correct size screen protector to fit their device and provide optimal protection against scratches, cracks, and other damage.