The ones I have are the Libra containers. 250s The S stands for Stackable. The quality is amazing even the packaging is great. I might even have some extras for sale at a very unreasonable price.Yep I believe they were designed to be used with that sump and fit where they angled the corner of the sump off.
Im not familiar with a stackable vertex container, the only ones I know of are the Libra containers. I’m sure they’re nice though, Vertex made really good quality products. It’s a shame they went under.