Genuine NuTone® model 391, 6-Gallon Filter Bags for a variety of NuTone Central Vac models dating back to the 1970's and still used today in the current Pure Power (PP-Series) Vac Tanks. The label on your vac tank will affirm whether it uses this bag. They come in a set of 3, but many folks buy 2-sets. I offer a substantial discount when purchasing multiple sets, and of course FREE SHIPPING to the United States of America.