A clip-on fan can be visualized as a small-sized variant of a rotating pedestal fan. It can be clipped on to the top-bar of the grow tent where it would move around and ensure proper circulation inside the tent. This, if you compare it to how things should normally be when you grow weed outdoors, results in the creation of a breeze inside the grow tent, which is great for keeping pests away and also good for ensuring that the stem and branches grow stronger. Hence a clip-on fan can be a great addition to your grow tent!