1 set of replacement filters with following : 1 x 20 Inch Big Blue Cation Resin Filter Cation exchange resin for hardness reduction & water softening Size 19 7/8 inch x 4.5 inch fits Big Blue filter housings Operational Temperature Range: 40°F-100°F Operational Pressure Range: 55-75 PSIIon exchange process – Water Softener Hard Water Filter uses ion resin mainly to reduce the Calcium, Magnesium in tap water, and works to remove low concentration of Iron in tap water, any iron 1 PPM and higher, it’s better to go with Iron filter. Prevent hard water scale: water softener filters are a great way to soften the water before your espresso machine or washing machine, protecting your appliances from scale build-up.Prolong the life of appliances- Softening the water before your appliance optimizes performance and reduces the chance of damage due to scale buildup.High Capacity – Water Softening Capacity: 4500 Grains of Hardness | Maximum flow – 4 GPM Total 1 filters, each individually wrapped.