Gizmo Breeze Fan Filter Attachments for 20 inch Box Fans Our simple cardboard frame design uses simple magnetic attachment flaps for a great fit and look. This product will not fit a 22", 24", or 26" box fan, and "or fans with controls on the back!" Gizmo Breeze is the number 1 choice for easy to use, indoor air filtration. Great Pleated MERV8 filter for maximum air flow. The included replaceable filter, is widely available anywhere furnace filters are sold.