1kg Castle Hot Tubs Non Chlorine Shock Granules for swimming pools, hot tubs and spas are ideal for regular oxidisation of water These are suitable for hot tubs running on chlorine or bromine Non chlorine shock restores sparkle and oxidises the water A genuine Castle Hot Tubs branded product, Grade A Non Chlorine Shock for use in spas and pools, top quality. These Non Chlorine Shock granules are rapid dissolving and have minimal impact on pH Keep PH levels between 7.2 and 7.6 and Chlorine Levels in a pool between 1-3 parts per million and hot tub 3-5 parts per million.