1 litre of virgin DI (deionizing) resin - widely regarded in the water fed pole industry as the best performing brand of Mixed Bed Deionisation Resin. Will 'polish off' your water to make it 100% pure. We recommend the use of this resin in an appropriate vessel with an RO beforehand in all but the softest water areas to prevent excessive usage of the DI resin. Suitable for most types of deionisation system including our own resin Vessels.