Fragmenter aims to preserve the local environment around the targeted torsion while retaining as little of the parent molecule as possible to reduce the computational demands of the calculation. However, oversimplification of the local chemical environment can result in fragments that inaccurately approximate the parent potential energy surface, which may lead to parameters that transfer poorly back to the parent molecule. It has been shown that the Wiberg bond order (WBO) provides a fast and robust measure of whether a torsion profile has been disrupted by fragmentation . BespokeFit then only accepts a proposed fragmentation if the WBO of the parent and proposed fragment agree to within a defined threshold (0.03 e by default).