Examples of hydrogen and helium retention efficiencies as a function of the mass transfer rate for a WD of 1 M_⊙. The prescriptions for the hydrogen retention efficiency η_H1 (solid line – NSKH07; HKN08) & η_H2 (dashed line – RBF09; Y10) and the helium retention efficiency η_He1 (dot-dashed line – Hachisu et al. 1999a; Kato & Hachisu 1999) & η_He2 (dotted line – Iben & Tutukov 1996) are shown in Appendix A. Note that the position of the peak of η_H2 is dependent on the exact prescription for Ṁ_cr. The mass transfer rate for hydrogen accretion is given by | Ṁ_comp |. For helium accretion this is Ṁ_He.