The Natural Impressions DIY-friendly, patented “rear lip” system makes it super-easy to stack the blocks. The contrasting face textures have natural rock finish on every block, so you won’t lose time trying to mix and match. Duo-stone allows you to build unreinforced walls up to 80cm in height because of the specialist engineered design. For straight wall, curved garden walling, garden bed segmentation, planter boxes, and veggie patches.