• The thermostatically controlled heat of GRO-QUICK electric soil warming cables gently speeds germination and seedling growth to produce large, healthy plants ready for transplanting • Use indoors or out to provide a head start to the regular growing season • Gro-Quick Soil Warming Cables have a built-in thermostat that automatically activates cables when soil temperature is below 74; • Speeds germination and seedling growth, producing large healthy plants, ready for transplanting • Use indoors or out to provide a jump start to your growing season • Dependable cables are covered with a tough, moisture-proof PVC jacket • All connections are sealed and waterproof • Available in 5 lengths • To determine which is best for you, match cable length to square footage of your planter • Place a minimum of 1 of soil below the cables, and approximately 3-4 of soil above the cables before the plants