From their website:
MBA's Direct line of terrain is adding World War II Bunkers, emplacements, fortifications and other terrain. The first of these items is the Eastern Front Bunker. This item has a removable roof that will allow you to put your troops base right in the bunker. It does not come painted.
The code for this Bunker is DIR-025, Eastern Front Bunker $8.95
This is another fine product that Miniature Building Authority offers as a DIRECT ONLY item. These items can only be obtained from us at the shows or via the website.