The Mitsubishi 072 filters I have cut open have a smooth, non corrugated center tube. After cutting the filter apart, you can crush the center tube with your thumb and forefinger flat. The Kia 504 filters and all of the K&N filters I have cut open have a ribbed/corrugated tube. After separating those filters and attempting to crush the center tube, it is nearly impossible to crush them with both hands. So I have experience with this test and I can tell you the reason is definitely to add strength to the center tube, in which it does very well.