Product review (4 stars): Decent product, needs some user love to get to 5 stars in-use.
They do their job reasonably well. What I don't think the pictures convey is that they are very thin packaging, approximately the same thickness that electronics or batteries come in. So all my vents blow them harder than they are intended to and the single little plastic clip they come with is mostly useless to help them stay in place. I have taken (since they are used to push air out from under something) to using a spacer between the bottom of the furniture above them and their top to keep them in place.