ResinTech RSM-25 is a sodium form macroporous strong acid cation resin. It is WQA Gold Seal Certified for use with potable water. Its high crosslinking results in very high selectivity for radium on a one-time use basis. It does not contain barium, is pH agnostic, and does not require a minimum sulfate concentration. RSM-25 is intended for radium removal from otherwise potable waters that contain modest concentrations of hardness ions such as calcium.