Harvest Right Filter Replacement Cartridges – 3pkPack of 3 filter cartridges for replacement in filtering system to help preserve the life of your pump and increase the performance of your freeze dryer. First use: Remove cartridge packaging, grip the top of cartridge and place into cartridge holder of Harvest Right filter. Firmly press in cartridge until it makes a firm seal. Cartridges should be replaced after approximately 15 20 uses, or sooner, depending on the quality of the oil. Oil Filtration