A protein complex conserved among eukaryotes that forms part of the kinetochore and plays an essential role in forming stable kinetochore-microtubule attachments. The complex contains proteins known in several species, including budding and fission yeasts, as Ndc80p, Nuf2p, Spc24p, and Spc25p. In vertebrates it is part of the outer plate of the kinetochore.