Depending on the desired design and design conditions, these tanks are equipped with a conical roof or a doomed roof, with or without anchors and stiffening rings, such as wind girders and/or a top corner ring. Naturally, these tanks can be provided with a spiral staircase, a cage ladder or a stairway. In terms of material, a form of duplex is often chosen. Due to this material being stronger than normal austenitic stainless steel variants, thin walls can be employed, which ensure for a more rapid, higher quality and affordable tank.