baseds on the number of cells in the plug tray, such as 24, 35,
36, 45, 50, 55, 60, 70, 72, 80, 82, 98, 104, 112, 128, 162,
200, 288, 392, 406, 512, etc.
plastic pots:1", 1.5", 2", 2.5", 3", 3.5", 4", 5.5", 6" etc.