These filters come with a template so that you can cut to exact size needed,  depending on model you own. These filters can trap larger particles, like lint,  and pet hair in some models of purifiers.. absorbs some common household gases and fumes from cleaning products, and deodorizes the air with carbon and zeolite.  They only need to be replaced about every 3 months and can be ordered online. I am very pleased with the ease and convenience of this product.