These Heat Mats speed seed germination and stimulate root growth by keeping soil at about 70º F. Here's a clever extra — instructions and growing tips are printed right on the mat, so you can't lose them. 9" x 19" mat holds a standard seed flat. 20-3/4" square mat holds two standard seed flats. 48" x 20" mat holds 4 flats. All sizes have 6-ft power cords.