MeshFilter

MeshFilter is a Unity component, it holds a mesh to be used on a GameObject.

MeshFilters have two properties which store meshes, and You should use In most cases, especially when making new vehicle parts.
 *   stores a 'unique' mesh which should only be used for that specific object
 * uses a shared mesh if possible, if other objects in the scene use the exact same mesh, they'll use the same asset. This saves performance on parts of which there are duplicates in the scene.

Note: MeshFilters won't render a mesh on their own, they need an associated MeshRenderer component. The MeshRenderer is also where the Material for the mesh is set.