Not perfect, but really really good
I have 2 of these to go along with a CD-275, and I'm adding a component stand to complete the suite. So I'm a Boltz fanboy. I love the industrial look and the finish is outstanding.
The only issue I think you need to be aware of is the torsion in the rods, at least when you have a few tied together. In my assembly, it added a good size curve to the rack. I had to fasten it to the wall to make sure it was stable enough for my collection. I wavered, but I couldn't really bring myself to deduct a star from quality for this. I'm not sure it's something within Boltz' control.
BTW: The description says this expansion adds space for 300 CDs, but it actually adds space for 600 CDs.
*BOLTZ NOTE: The 12" expansion kit will add space for 300 CDs, the 24" (CDEXP-T) expansion will add space for 600 CDs