Instruct: Classify the given review as either positive or negative.
Query: I consider this product very necessary.

This product doesn't come in strips. It comes in a quite generous roll of the material. You cut it to the necessary dimensions and install right behind the vents in your house. I've been using this product for a long time and when I remove the old ones, you realize how much crap it picks up that you would otherwise be breathing. I suffer from allergies and I have been able to control my reactions in my home.