LOD Replacers are packages of the ".lod" data files (LODs) necessary to view objects that are not in the foreground; that is objects that are "distant" in the middle or back ground, also known as "Viewable While Distant" (VWD) objects. Not all replacer packages contain all the files related to LODs, such as meshes, textures, normal maps, and statics. Many include some of the optimized "_far.nif" (low polygon mesh) files lacking in the vanilla game to make objects visible from a distance, but not necessarily the same ones. (A "_far.nif" file is required to build a ".lod" file.) They are intended to overwrite the vanilla versions of the files they do contain, and generally work with the remaining vanilla versions of the related files, to varying degrees of success.