Plastic. Light design, favorably characterized by ease of installation. The duration of their operation is impressive and is at least 40-50 years. For installation, you do not need to use special equipment. It is worth noting that the ease of such a septic tank is sometimes its weak quality. The fact is that he can trite “surfacing” to the surface. To prevent this, the septic tank is concreted during the installation process or use a special “anchor”.