Multi-Walled CNTs (MWCNTs, MWNTs) are hollow, cylindrically shaped allotropes of carbon that have a high aspect ratio (length to diameter ratio). Name of Multi-Walled CNTs is derived from their structure and the walls are formed by multiple one-atom-thick sheets of carbon. Multi-Walled CNTs consist of multiple rolled layers of concentric nanotubes of graphene inside other nanotubes. Two main models can be used to describe the structures of Multi-Walled CNTs. The Russian doll model of Multi-Walled CNTs consists of sheets of graphite arranged in concentric cylinders. In the Parchment model, a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled newspaper. The properties of Multi-Walled CNTs are unique because they come in a complex array of forms and each concentric nanotube can have a different structure, there are a variety of sequential arrangements.The simplest sequence is when concentric layers are identical but different in diameter. However, mixed variants are possible, consisting of two or more types of concentric Carbon Nanotubes (CNTs) arranged in different orders. These can have either regular layering or random layering. The structure of the carbon nanotubes influences its properties including electrical and thermal conductivity, density, and lattice structure. Both type and diameter are important. The wider the diameter of the carbon nanotube (CNTs), the more it behaves like graphite. The narrower the diameter of the Carbon Nanotubes (CNTs), the more its intrinsic properties depends upon its specific type.