Source frame merger-rate density for BH-BH binaries. We note that there is virtually no change of the rate at any redshift for models with (M10) and without (M1) pair-instability pulsation supernovae and pair-instability supernovae. For reference, we plotted the horizon distance for our most massive BH-BH merger in model M10 (M_tot ≈ 80 M_⊙; see Fig. 3). We also show our pessimistic model with high natal kicks (M3).