Distribution of ZAMS binary orbital period, p, primary mass, M₁, and the final primary BH spin of systems evolving thorough the CHE channel to become merging BBHs in our fiducial model. In this sample we only include BBH systems with inspiral times less than the age of the Universe. Different markers differentiate metallicity regimes according to the legend. For visualisation purposes, we capped the color bar at a_BH1 = 0.7 even though there are BHs approaching the general relativistic limit a_BH1 = 1. Although binaries with p <  1 day do tidally spin up and evolve through CHE, they later undergo mass loss due to PPISN which depletes the WR star of its angular momentum reservoir.