The Omnipure K-Series K5520 inline filter is a 1 micron carbon block inline filter. This filter can be used as a post R.O. filter. The filter has 1/4 FPT and 1/4 QC fittings. This filter can also be used in ice makers, refrigerators, beverage equipment, drinking fountains, under the counter systems, R.O.Systems and in conjunction with purification systems. It also aids in the removal of sediment, taste, odor and chlorine. Dimensions: 2.5" W X 10" L Rating: 1 Micron Rating Flow Rate: .5 GPM Maximum Pressure: 125 PSI Maximum Temperature: 100 F Service Life: 1 Year or 2500 Gallons Filtration Media: Carbon Block Reduces: Chlorine Taste Odor Reduces: Particulates Class 1 Fitting Size: 1/4" FPT and 1/4" QC National Pipe Thread (NPT) Size Measured Against a Ruler* Actual Diameter (Inches) National Pipe Thread (NPT) (Fractional) 0.405" 1/8" 0.540" 1/4" 0.675" 3/8" 0.840" 1/2" *NOTE: A very common misconception is that a 1/4" NPT measures as 1/4 inch on a ruler or tape measurer. However, that is not the case. NPT will measure larger in diameter. Above is a sizing reference to help clarify.