This pack includes all the filter pads and media you need for your Professional II filter: The set contains: Ehfimech x 2 litres. Removes all coarse and fine dirt particles from the water Substratpro x 4 litres. For quick colonisation of bacteria and faster decomposition of toxins. Coarse filter pad x 1. Large pore sponge giving bio-mechanical filtration and even water flow-through. Fine filtration x 1. Before the water re-enters your aquarium fine dirt particles are trapped in the fine filter pad