The FOSC 400 A4 fiber optic splice closure is the smallest enclosure in the FOSC 400 series. It serves as a fundamental solution designed for constructing both trunk and distribution fiber optic networks. In trunk networks, the closure is utilized in a through version, whereas in distribution networks, it is employed in a branching version, enabling branched connections of fiber optic cables. It is primarily installed in cable vaults and utilized for establishing aerial fiber optic networks.