Growers Supply Company Humidity Domes for 8-Inch by 12-Inch by 3-Inch Perma-Nest Plant Trays, Pack of 4 Stackable for easy storage; reusable Easy to clean; white in color Rugged polystyrene; hot and cold sterilized Retains heat and moisture Measures 12 inches in length by 8 inches in width by 3-1/4 inches in height