For NORMALPNO DLPNO-CCSD(T 0 ), the MAD of reaction energies with respect to TIGHTPNO DLPNO-CCSD(T 0 ) slightly increases with the basis set size, e.g., from 0.37 kJ • mol -1 for def2-TZVP to 0.51 kJ • mol -1 for def2-QZVP, whereas the MAD of barrier heights decreases, e.g., from 0.54 kJ • mol -1 for def2-TZVP to 0.29 kJ • mol -1 for def2-QZVP. A similar tendency is also apparent for pair-selected multi-level DLPNO-CCSD(T 0 ) with a target accuracy of TIGHTPNO, the MAD of reaction energies and barrier heights increases from def-TZVP with 0.14 kJ • mol -1 and 0.22 kJ • mol -1 to def2-QZVP with 0.44 kJ • mol -1 and 0.57 kJ • mol -1 , respectively. For a target accuracy of NORMALPNO, the MADs are significantly increased up to more than 3 kJ • mol -1 . This increase is mainly due to one outlier, reaction 7, with an error of 30.7 kJ • mol -1 for the reaction energy and 21.9 kJ • mol -1 for the barrier height. Excluding reaction 7 decreases the MADs for both reaction energies and barrier heights to about 1 kJ • mol -1 which is in better agreement with the results for def2-TZVP. This large error for reaction 7 is mainly related to the DLPNO-(T 0 ) contribution as discussed later in this section for the inclusion of diffuse basis functions.