The χ _eff distribution as inferred by a BimodalGaussian effective spin model, defined as the sum of two Gaussians (see Appendix A). Solid blue lines denote the 90% credible intervals, while blue light curves are select individual draws from the posterior. For reference, the dashed black curve shows the mean χ _eff distribution as inferred using a single Gaussian. Both results are consistent with one another, indicating no evidence for bimodal features, narrow or otherwise, in the binary black hole χ _eff distribution.