(M_WD,P_orb)–diagram for all the studied LMXB systems which produced a detached He WD. The initial parameters were chosen from: M₂ = 1.2−1.6 M_⊙, M_NS = 1.3−1.9 M_⊙, γ =2−5, and ϵ = 0.1−0.9. The thick curve (TS99) represents the analytical expression given in Tauris & Savonije (1999) for Z = 0.02 (which was derived only for P_orb ≳ 1day, but here for illustration extended down to smaller values of P_orb). The green diamonds represent observed MSP systems with He WDs and P_orb< 15h (i.e. similar to the solutions and partly the intermediate systems of our modelling). The region where the analytical expression is uncertain is for P_orb< 2 days (and M_WD ≲ 0.20 M_⊙). Although our calculations show a larger spread of the systems in this region the modelling of this correlation is still surprisingly robust – see text.