A component contains one or more primitives that define the shape of the component. A primitive specifies a geometric construct, such as a cylinder or a sphere or refers to another component in the MDL model. Primitives can be modified by parameters such as color, style and translucency. Most primitives include a Data section that specifies the coordinates of the primitive.
| Cylinder | Extrusion | Helix |
| Polygon | PolygonMesh | Revolve |
| Skin | Sphere | Refer |