ANPHSIN 4-Pack 6 Inch Prefilter for 6" Carbon Filter - Electrostatic Cotton Replacement Prefilter Sleeve Covers for 6" Air Carbon Filter of Grow Tents Grow Rooms (White)

The ones I got actually had a 10inch diameter not 6 inch. Still made them fit with the help of two safety pins. Functional but not great.

Had to stretch to the point of ripping to get onto a phresh 6" filter.Very thin, not like what comes with most filters.Not very happy.