Aprilaire Whole Home Humidifier Installation Kit for Aprilaire Models 400, 500, 600 with Automatic Control, Silver, Evaporative, 2.94 Pounds

Everything you need except for tools.

It would be nice to get a longer length of wire. It is not a complete kit and will require wire nuts as well. I recommend not using the piercing valve or plastic tube as it can get brittle and leak. It’s best to get its own dedicated valve and using copper tube. As the supplies tube is only for cold water.

As mentioned by other reviewers, you don't get a whole lot. They only provide a bare minimum and even less. The flex duct is too short. They expect you to install the humidifier and the cold air duct right next to each other. If you install a different way, then the flex duct will not be enough. I ended up buying two elbow ducts. The four screws they provided is for humidifier only. For the switch, you need your own screws. The four wire connectors are also not enough. But they do provide longer hose and pipe than you need. You could get your own from a hardware store for a lot cheaper and more than you need.

My "go to" brand.

So, the 6" duct work is about 3' long. That is to make the bend and bridge the gap between humidifier and the return. That might be ok for some installations, but not most. Wires are not overly generous. Basically, you could do better buying items separately. There is absolutely no instructions or labels for the items to understand how or for what they are to be used. Wiring needed to be stripped to see what is what.