Gravitational wave (GW) detections of binary black hole (BH) mergers have begun to sample the cosmic BH mass distribution. The evolution single stellar cores predicts a gap in distribution due pair-instability supernova (PISN). Determining upper and lower edges can be useful for interpreting GW from merging BHs. We use \MESA\ evolve single, non-rotating, massive helium with metallicity $Z = 10^...