Product review (4 stars): Good kit
This kit has everything you need to install the humidifier. If you are somewhat handy, you can wire the solenoid and humidistat to the control board directly and not need the sail switch and the transformer. I am no HVAC expert but I have a circuit as follows: one wire to the power terminal on the board ->humidistat ->solenoid ->  fan terminal on the board (for some reason the W1 would not work) and it works great. Anytime the fan turns on, it activates the humidifier if the humidity is below the set level on the humidistat. In theory I could have looked around the local hardware stores and found the separate parts for cheaper, but not much cheaper. I also installed an in-line filter for the water supply as there is quite a bit of sediment in the water here.