Evolution of the relations between the parameters and types of components in the progenitors of AM CVn stars. Upper panel: precursors of AM CVns generated by BSE at ZAMS. (a) Relation between the masses of progenitors of WDs and initial P_orb; (b) relation between the masses of progenitors of He stars and P_orb; (c) relation between the masses of progenitors of WDs and He stars. Middle panel: the binaries immediately prior to the first RLOF. Panels (a)–(c): same as in the upper panel. Dots represent the binaries which pass through CE, crosses indicate the systems with stable RLOF. Lower panel: the binaries prior to the second RLOF. (a) Relation between the masses of WDs (M_WD) and P_orb; (b) relation between the masses of pre-He stars and P_orb; (c) relation between M_WD and the masses of pre-He stars. The colour scale in the upper panel shows orbital eccentricities; in the middle and lower panels, colours indicate the types of systems according to BSE: 1 – MS star, 2 – Hertzsprung gap star, 3 – first-ascent red giant, 4 – core He burning giant, 5 – star at E-AGB, 6 – TP-AGB star, 7 – naked He star, 8 – He star in the Hertzsprung gap, 9 – naked He-(sub)giant, 10 – He WD, 11 – CO WD, 12 – ONe WD. In the lower panel (c) the colors of symbols are not related to BSE.