This air filter clip is specially designed for 20 inch furnace filter. If you often use the box fan with filter and are troubled about how to secure it, so this clip will perfectly solve your problem. These clips are suitable for any situation where a box fan furnace filter is needed, whether it is at home, a shop or a woodworking studio. It can help you better secure the furnace filter.It is easy to install and remove, it's simple and beautiful.