Blue Horizons Rapid Shock The size of this product is 6 x 2Kg. Rapid Shock is a quick dissolving, chlorine shock calcium hypochlorite, for either remedial or regular shock dosing of your pool or spa. pH correction using pH - (dry acid) may be required. Always read and adhere to the instructions on the pack and never directly mix chemicals. Shock dose your pool prior to winterisation and then add Kleenpool longlife algaecide to keep your pool algae free for up to six months. You can then add Kleenpool in the spring to help keep your pool algae free for the summer season too. Don't forget, the price you see is the price you pay not a penny more. We sell chemicals cheap, not cheap chemicals!