Easy Scenery (EZ)
The main pieces/walls are 75mm x 75mm (3inch square) Sections with 'connectors' for each piece and 'fillers' to fill any connection holes you're not using. You can lay them all side by side or stack them up as high as you like. Add them to other sets.
While the Easy Scenery Kits can work with the legacy castle wall sections, and have been designed so the could fit beside them, they work best with all EZ sections and kits as they have the same fitting method which allows far greater variation and allows us to put any combination together. You could run a wall across a table which started as a medieval castle and worked it's way through different regional stone types of styles all the way to a fantasy tree city and it will still all fit!