It does just what it says--it adds 6" to the upper tier attachment so that it becomes the same height as the bottom rack. The only thing that didn't make sense to me was that it comes with 2 center poles. The one pole goes under the pole of the upper tier which you would expect it to do. but the other one you have to switch out with the pole of the bottom rack to make it more sturdier to support the upper rack. Which, in doing that, does make sense because you are adding more height and it does make it sturdier, but now I have the pole from the bottom rack and I have nothing to do with it! You think they would make it with a broader pole for the bottom system and then just sell the extension kit with 1 upper add on pole, so then it would be cheaper too. But I still love it and highly recommend the whole thing!!
The upper tier extension kit provides a stable opportunity to store and display a lot more product. I have been able to place all of the embellishemts on the base unit with extension plus a mini unit. I love it and would buy it again! I was pleased that the extension is adequate for 12 inch items and that it is not at risk of falling over!