Planters' Pride RZ.HEAT4 Heat Mat for Propogation and Cloning, 20 x 48-Inch The only ETL Certified heat mat on the market that conforms to UL Standards and is certified to CSA Standards Warms root zone 10 Degree - 20 Degree above room temperature to increase success rates of seedlings, clones and cuttings Speeds germination and encourages stronger root growth Fits under 4 standard 10 x 20 - Inch trays Durable, waterproof construction