  Using the different versions of phenomenological proximity potential as well
as other parametrizations within the proximity concept, we perform a detailed
comparative study of fusion barriers for asymmetric colliding nuclei with
asymmetry parameter as high as 0.23. In all, 12 different proximity potentials
are robust against the experimental data of 60 reactions. Our detailed study
reveals that the surface energy coefficient as well as radius of the colliding
nuclei depend significantly on the asymmetry parameter. All models are able to
explain the fusion barrier heights within $\pm10%$ on the average. The
potentials due to Bass 80, AW 95, and Denisov DP explain nicely the fusion
cross sections at above- as well as below-barrier energies.
