The seed tray inserts are used for sowing seeds in individual cells. This allows you to grow healthy plants from the seed without competition for nutrients from other plants. This also means that there will be no weed plants to provide competition over nutrients. The plants can be grown in the cell until they are mature enough to be placed in a communal pot. The seed tray inserts are made from recycled plastic and are fully recyclable. They will fit most standard seed trays.