Sorry guys, it's gone.
I saw it last night but thought about how those cantilever boxes can be a ***** to get things out of when they don't quite clear the lower tier. The other negative is it's higher at the outer tray so the lower inside trays are even more inaccessible. Then I saw the dimensions and figured at 17" wide it would fit on the side and likely bolt into the push handle lugs of a roller. I visited the ad about a half hour later and it was still there. Looking at it from the side like that I figured access wouldn't be so bad and it really adds a lot of storage so I bought it.
I saw this post when I got home last night and had to laugh. I sent the seller a link too and he also got a laugh but maybe thinks he priced it too low

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My rational was, I already have 2 hanging socket trays on the front of my main box, one along the side (on the inside) and a fourth one inside on the partition that runs lengthways in the centre of the top open area. I also have a twist lock socket rail attached to the front face of that box. This little add on box will add more storage than all 5 of those put together. …..and the price was right.