Status report on the Special Interest Group on Component & Separate Technical Unit work on UN R158 and UN R159. The SIG-C&STU is developing proposals to add Component and Separate Technical Unit approval routes to UN R151, UN R158, UN R159, and UN R166. For UN R159, Supplement 4 is under review with documents at GRSG-132. For UN R158, a Proposal for Supplement 7 is in development. The group requests feedback on structural approaches and timelines for working document submissions by January 2027.