ResinTech CNS-F is a fine mesh, non-solvent, strong acid cation resin in sodium form. It is Black in color and made from standard crosslinked gel. CNS-F is Gold Seal Certified by the WQA for potable water applications. CNS-F is intended for residential softening applications with high levels of iron in the feedwater, that do not contain significant chlorine residual, and where resin bed depth is less than ideal.