Product review (5 stars): Works great and installs easy - No strainer needed.
Honestly, I was on the fence between 4 and 5 stars. The only reason I was thinking about 4 stars is the lack of any instructions/documentation either in the box or online on the vendor/manufacturer website. However a basic Google search leads to a plethora of reviews and a few videos. The good news is that the contents were exactly as in the picture (not the thumbnail that shows a black housing but the picture on the product's webpage). Mine was a brass colored valve that came with a compression nut and a ferrule on the inlet side of the valve. You could either re-use your existing compression nut or use the one with the valve. I reused mine from the old valve which was an OEM one. I did have to loosen the big nut and rotate the housing around in order to match it up with my inlet/outlet water pipes.
One BIG difference between the 'new version' of the valve that I got and some earlier 'most helpful' reviews is that the new valve has a built in metal strainer. You DONT need to buy a separate black plastic strainer (Aprilaire 4004 Humidifier Drain Type In-Line Strainer). You can check out this video where the presenter clearly says that the valve has a built in metallic strainer. http://video.aprilaireparts.com/v/1043089725/aprilaire-4040-solenoid-valve/
Some of the 'most helpful' reviews are dated. I don't intend to trash the earlier reviews. I only want to share what I realized. Installation was very easy and it went exactly as shown in the video. I was done in less than 30 mins. I also installed the maintenance kit which took another 45 mins or so. Time well spent and money well saved.