Possible parameter space of binary radio pulsars in a M₂ − P_orb diagram for different η. The upperward-pointing red and downward-pointin green triangles, blue squares, and cyan stars indicate observed binary pulsars with He WDs, CO WDs, MSs, and NSs. The data are taken from the ANTF pulsar catalog (Manchester et al. 2005). The black dots are the results we calculated for binary radio pulsars with giant companions.