Exhaust fans with high CFM ratings can create too much negative air pressure that the canvas walls flex inward, encroaching on your precious grow space. The high CFM (Cubic Feet Per Minute) kit is to help prevent your indoor grow tent walls from sucking in due to high amounts of negative pressure from exhaust systems. These Gorilla strong poles will get you back to growing in no time. These awesome kits are made with Gorilla's high standards and easily snap into place horizontally on the frame of your Gorilla Grow Tent. The bars are made from the same steel that has made the Gorilla Grow Tent brand famous and features custom-molded, high-density plastic clips that lock into place to ensure strength.