Provides additional support and length. Provides additional hip support via wider cushion design. Integrated rear storage. Battery cover with support (860201720) required for REV Gen4 (Narrow) without battery. Battery cover (511001210) required for REV Gen4 (Narrow) with battery. 2 Summit seat posts (510006693) required for installation on REV Gen4 (Narrow) Summit 2020 and prior. 2 seat post (510007122) required for installation on REV Gen4 (Narrow) Summit and all Sport models, 2021 and up. Not compatible with Battery Cover (860201407). - REV Gen5 (Trail), Neo, REV Gen4 16"