The S-IVB (sometimes S-4B, always pronounced "ess four bee") was built by the Douglas Aircraft Company and served as the third stage on the Saturn V and second stage on the Saturn IB.
S-IVB (kadang-kadang S4b, selalu diucapkan "ess four bee") dibangun oleh Douglas Aircraft Company dan menjabat sebagai tahap ketiga pada Saturn V dan tahap kedua pada Saturnus IB.