Humity, Germination, Propagation Dome for Standard 1020 Tray Size: 11" x 21" x 2-1/2" deep. Compatible with most seed trays/ flats Maintains high and even humidity/ temperature levels Speeds germination and improves seedling success Made of clear plastic to allow light in -- prevents moisture from escaping! Compatible with most seed trays/ flats Reusable -- will last several seasons. Fits ALL standard 1020 seed flats.