However, for some relative energies, the error with respect to canonical CCSD(T) is lower for the multi-level variant, e.g., for the reaction energies of reactions 4 and 6. In total, the MADs only differ insignificantly. Namely, the MADs of reaction energies amount to 0.53 kJ • mol for multi-level DLPNO-CCSD(T 0 ) with a target accuracy of TIGHTPNO and 0.49 kJ • mol -1 for TIGHTPNO DLPNO-CCSD(T 0 ) while the MADs of barrier heights amount to 1.77 kJ • mol -1 and 1.63 kJ • mol -1 , respectively. Consequently, the error of the pair-selected multi-level approach is dominated by the approximations introduced through TIGHTPNO DLPNO-CCSD(T 0 ).