Designed for Tetra EX 600/700/800 Plus external filters The original insert made of synthetic non-woven fabric Markov Stops minor impurities Protects the filter head Placed as the last insert (at the very top) Replacement every 4-8 weeks High quality TETRA TEC - FF FilterFloss (Smal Size) is an original cartridge made of synthetic non-woven fabric designed for external filters of the EX series. Place the non-woven fabric in the filter at the very top as the last filter element. The filter fabric also protects the filter head, including the impeller, against various types of contamination. NOTE: to maintain optimal filtration, replace the non-woven fabric every 4-8 weeks, depending on the degree of soiling. The cartridge should be rinsed in warm water before use.