The SUNPACK SUNPAD 8.875in x 19.5in heat mat is perfect for any gardener looking to start seeds or root cuttings indoors. From beginners to professionals, this mat is reliable and easy to use. It warms the root zone 10-20 degrees Fahrenheit above the ambient air temperature, cultivating the perfect environment for cuttings and seedlings. They are waterproof and allow gardeners to have peace of mind that they are creating the perfect environment for their plants. This size will perfectly fit one standard-sized 1020 tray.