We show that if
$(X, T)$ is an extension of an aperiodic subshift (a subsystem of
$(\mathop{\{ 1, 2, \ldots , l\} }\nolimits ^{ \mathbb{Z} } , \mathrm{shift} )$ for some
$l\in \mathbb{N} $) and has mean dimension
$\mathrm{mdim} (X, T)\lt (D/ 2), D\in \mathbb{N} $, then it can be equivariantly embedded in
$(\mathop{(\mathop{[0, 1] }\nolimits ^{D} )}\nolimits ^{ \mathbb{Z} } , \mathrm{shift} )$. The result is sharp. If
$(X, T)$ is an extension of an aperiodic zero-dimensional system then it can be equivariantly embedded in
$(\mathop{(\mathop{[0, 1] }\nolimits ^{D+ 1} )}\nolimits ^{ \mathbb{Z} } , \mathrm{shift} )$.