The popularity of Density Functional Theory (DFT) in chemical research has led to the creation of so many density functional approximations (DFAs) that the field has been described as a "zoo", and the popularity of a method does not always correspond with its accuracy. Trying to find one that is appropriate for a given application among the wide variety available is simplified through the process of benchmarking, which involves comparing lower-level methods to highly accurate reference data. Coupled Cluster Singles Doubles with Perturbative Triples [CCSD(T)] 3 is considered the "gold standard" of chemical accuracy for theoretically calculated barrier heights and reaction energies. In practice, this is too expensive beyond small molecules, and a range of local approximations have been developed to reduce the cost of the coupled cluster treatment. One popular method is the domain-based local pair natural orbital approximation [DLPNO-CCSD(T)], which scales linearly with system size and can therefore be applied to much larger systems than canonical CCSD(T). The efficiency of the DLPNO approximation comes from the fact that not all electron pairs in the system are treated at the Coupled Cluster level, with a range of thresholds involved in pruning the electron pairs and pair natural orbitals (PNOs) to be included in the final correlation calculation. Three pre-defined sets of values for each threshold giving increasing levels of accuracy (LoosePNO, Nor-malPNO and TightPNO) make the method extremely user friendly; a fourth set (Very-TightPNO) has also been created for particularly challenging applications, but is less frequently used as it is not yet available as a simple keyword in the ORCA software like the others.