Dop Smart/Mono/Twin Rautitan link The Dop Smart, Mono and Twin Rautitan links are all types of plumbing systems specifically designed for use in commercial and residential applications. The Dop Smart system is a multi-layer plumbing assembly that is designed to reduce the amount of water needed to run plumbing fixtures. The Mono system is a single-layer system designed to provide a cost-effective solution for running water pipes. The Twin Rautitan system is a two-layer system made from an innovative composite material that offers superior strength and durability. All of these systems provide a reliable and efficient way to run plumbing systems in a variety of commercial and residential applications.