  The Letter of Wang et al. \cite{wan} is related to the recently discovered
vanishing of the second magnetization peak (SMP) in high-$T_c$ superconductors
reducing the sample size \cite{kope1,kope2,gal}. This phenomenon has been
interpreted \cite{kope1,kope2,gal} in terms of thermomagnetic instability (TMI)
effects. The TMI approach has also been adopted by Wang et al. in their
previous work \cite{wan2} on the critical sample size temperature dependence
$R_{cr}(T)$ measured in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) single
crystals. In contrast, in the recently published Letter \cite{wan} the authors
claimed that the $R_{cr}(T)$ obtained for Bi2212 crystals is at odds with the
TMI model and proposed an alternative explanation of the results assuming that
the SMP vanishes as the sample width (or diameter) becomes smaller than the
in-plane vortex correlation length $R_c^{2D}(T) \sim J_c(T)^{-1/2}$, where
$J_c(T)$ is the critical current density. We demonstrate below that the authors
conclusion is misleading.
