Jiffy Grow Dome Lid Can Be Used With Plant Starter Trays And Cell Packs. Helps keep humidity and warmth close to the plant. Useful for new plant cuttings that have no roots, yet. Keep an eye on it so you don't get too wet or boil your plants. 21" x 10.5" x 2.25" When combined with the trays and starter cells the entire set up is about 5" tall.