Apollo Horticulture AH GMK-1 Germination Seedling Seed Starter Kit with Humidity Dome and Heat Mat, Black and Clear 1 - Apollo Horticulture Seedling Starter Kit with Heat Mat Dimensions: 21.25" x 11" x 9.50" / Heat Mat: 9"x 20" 72-cell Seedling Inserts with 3 vent points for optimal airflow Controls humidity under a 7.23" dome cover, providing warmth to the planting bed Package Includes: 1 - Dome Cover / 1 - Seedling Tray / 1 - Water Tray / 3 - Plastic Vents / 1 - Heat Mat