  In this paper we consider Bernoulli percolation on an infinite connected
bounded degrees graph $G$. Assuming the uniqueness of the infinite open cluster
and a quasi-multiplicativity of crossing probabilities, we prove the existence
of Kesten's incipient infinite cluster. We show that our assumptions are
satisfied if $G$ is a slab $\mathbb Z^2\times\{0,\ldots,k\}^{d-2}$ ($d\geq 2$,
$k\geq 0$). We also argue that the quasi-multiplicativity assumption is
fulfilled for $G=\mathbb Z^d$ if and only if $d<6$.
