Assembly vs kits vs real product.

I believe that "assembly" just means the part you're trying to buy such as......

The red and yellow brake buttons....... the piece behind the dash is the "assembly"

Its hard to explain some things lol.......

 

When an automotive part is sold as an "assembly," it means you're buying something that's composed of multiple individual parts that are already put together to form some larger component. You may or may not be able to buy each of the individual parts separately. It's frustrating when you have to buy an expensive assembly to get the one piece of it that actually broke. In your example, it's probably being called an assembly because it includes both the valve and ECU.

 

The part numbers break down what you have. The "X" at the end means that it is a reman part by HALDEX, since this is a WABCO valve but is sold as a reman by Haldex, that would be the difference. WABCO also sells reman as "X" or "7" at the end but then it would have been rebuilt by them vs the one you are looking at is a WABCO valve rebuilt by Haldex. I think that's the major difference here.