Good House Range Hood Filter R Type This is a set of 13 filters: 10 unopened and 3 opened. I've used these filters for a long time, but I no longer need them since I replaced my ventilation fan, so I'm selling them. ~The following is a quote from the product description~ It's more important to prevent the range hood from getting dirty than to clean it after it's already dirty. The easiest and most effective way to do this is with a range hood filter. Oil absorption rate of 90% or more These ventilation fan filters are made of flame-retardant mixed fibers that absorb oil very well. Replacing them regularly every 2-3 months will keep the inside of your range hood almost clean.