The 5Kg brick expands to make 75-litres, and the 1Kg expands to 15-litres. This is enough to fill the following: SMALL POTS 9cm (3½ inch): 185 from 5Kg, 37 from 1Kg MEDIUM POTS 15cm (6 inch): 50 from 5Kg, 10 from 1Kg SEED TRAYS: 21 from 5Kg, 4 from 1Kg.