Reverse Osmosis Revolution Dual Stage Whole House Water Purification System with Sediment and CTO Filters, with 3/4 Powerful 2 Stage Whole House Water Purification system with 3/4 Comes with 1 Year filter supply 1st Stage: Quick-Connect 5 micron sediment filter. Dust, dirt, silt, sand, rust and scale particles are trapped here in a filter which also extends the life of the system. 2nd Stage: Premium 5 Micron High Dirt Capacity CTO Block Filter (10"x2.5") Whole House filter system uses standard 10"x2.5" cartridges