Yuhui  C-SS-SST is a gel-type strong acid cation (SAC) exchange resin based on sulfonated styrene-divinylbenzene (DVB) copolymers with standard Gaussian particle size distribution. Due to using the surface sulfonation technology, 90%+ functional groups of C-SS-SST are on the surface of resin beads, which offers the outstanding kinetics on both capturing and eluting ions, especially for iron. C-SS-SST is developed to be used for residential regenerable water softeners especially for the water with high iron content.