Use with seedling trays for extra support or with leakproof trays for bottom-watering. Holes spaced for canopy development. 24-cell flats are recommended for cucumber, eggplant, melons, pumpkin, squash, tomatoes, and large-seeded herbs and flowers. Compatibility: Use with all Johnny's trays except Lightweight Shallow Trays (white) and Lightweight Shallow Trays (with Holes, black).