  The slice-Bennequin inequality states an upper bound for the self-linking
number of a knot in terms of its four-ball genus. The $s$-Bennequin and
$\tau$-Bennequin inequalities provide upper bounds on the self-linking number
of a knot in terms of the Rasmussen $s$ invariant and the Ozsv\'ath-Szab\'o
$\tau$ invariant. We exhibit examples in which the difference between
self-linking number and four-ball genus grows arbitrarily large, whereas the
$s$-Bennequin inequality and the $\tau$-Bennequin inequality are both sharp.
