Non-catalytic component of the exosome, which is a complex involved in RNA degradation. Contributes to the structuring of the Rrp41 active site. Component of the archaeal exosome complex. Forms a hexameric ring-like arrangement composed of 3 Rrp41-Rrp42 heterodimers. The hexameric ring associates with a trimer of Rrp4 and/or Csl4 subunits. Belongs to the RNase PH family. Rrp42 subfamily. Truncated N-terminus.