With the same M08-HX functional, the overall accuracy of CNEO-TST, which does not need scaling, is again notably better than that of CTST with the standard scale factor. The good performance can be partially rationalized from the transition structure geometries. We find that the geometry corresponding to the maximum potential on the CNEO effective potential energy profile agrees better with geometry at the maximum of the Born-Oppenheimer ∆V G a curve than with the geometry at the maximum of the V MEP curve. This is illustrated in The CNEO-TST rate constants have optimal accuracy near room temperature due to the incorporation of ZPE and shallow tunneling effects. At lower temperatures, where deep tunneling effects become more pronounced, CNEO-TST again starts to underestimate the rate constants. At higher temperatures, the CNEO-TST curve exhibits a parallel behavior to that of CVT/SCT with the SRP scale factor for the transition structure, albeit with an overestimation by roughly a factor of two.