Warms root area approximately 10°F - 20°F over ambient temperature to improve germination process. Helps gardeners have better success rates with seedlings and cuttings. Perfect for two standard 10 in x 20 in propagation trays. Heavy-duty construction makes this mat very durable. More than 20% larger than competitive mats. This allows even warming of your entire tray. Dimensions: 20 in x 20 in.