The initial model was followed by the CRJ100 ER subvariant, featuring 20 percent greater range, and the CRJ100 LR subvariant, which possessed 40 percent more range than the standard CRJ100. This sub-variant was developed with the purpose of more closely conforming with the requirements of both corporate and executive operators. A cargo door retrofit has been developed for the installation of former passenger-configured aircraft to extend the useful life of early-built CRJ100s.[12]