The Omnipure K-Series (K2320) filter is a post carbon filter for RO systems. This filter helps in removing all types of contaminants in your water including sediment, bad taste, water odor, and chlorine taste and odor. It is a 1 micron filter and comes in 1/4" FPT, 1/4" QC, and 3/8" QC fittings.
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.