Sorry ggsteve, for some reason I missed your question, total DIY, heatsink was something I had laying around, the resistor is a 24 ohm 50W unit mounted to the heatsink with heatsink compound and most expensive part is the temp sensor mounted about one inch above the bottom (2455RBV84690007 Honeywell Thermostats) about $25 closes at 1.7C opens at 12.8C, I feed 24vdc out to it with 18awg zipcord and a little insulation inside to hold the heat.