Get a jump start on spring planting! This Seedling Heat Mat is just the right size. It's 20" X 20" which makes it large enough for several of the Jiffy Trays. It warms up the rooting area 10-20 degrees over ambient temperature which translates to faster germination, higher success rates and faster growth for quicker transplanting. Helpful tips on watering, lighting and transplanting are printed right on the mat--you'll never lose the instructions! The mat is waterproof, 120 volt, 50 watts. And we just found out that it also aids in the process of beermaking.