They are absolutely not worth your money. They have a terrible reputation, and are poorly made. (open one up and you will know what I mean)

As has been mentioned, the hydrofarm thermostat is the same price and has a much better track record. there are still much better thermostats available, but the hydrofarm will do the job.

http://www.amazon.com/Hydrofarm-MTPR.../dp/B000NZZG3S