WEBPurolite C-100-E Cation Resin, High purity, premium grade, prewashed, strong acid gel-type cation exchange resin. For directions and other tanks sizes , see Resin Replacement Guide. NOTE: You will want a good funnel to help pour the resin into your tank. Typical Physical and Chemical Characteristics: • Total Capacity, Na+ Form (min.): 1.9 eg/l.