Give your seeds a quick start! The Jiffy-Gro® Heat Mat give continuous even heat! The mat provides the optimum seed starting temperature for your plants. You can start your seeds with the Jiffy-Gro Heat Mat 4 to 16 weeks prior to above average planting dates for your area. Simply follow the specific directions on your seed packet. Remove Jiffy-Gro® heat mat when seeds sprout. The Mat will feel lukewarm to touch, not hot. Mat size: 18.375"(46.67cm) x 8.5"(21.59cm). UL listed.