Let $$A$$ be a finite subset of $$\mathbb{Z}^n$$, which generates $$\mathbb{Z}^n$$ additively. We provide a precise description of the $$N$$-fold sumsets $$NA$$ for $$N$$ sufficiently large, with some explicit bounds on sufficiently large." For example if $$A$$ has exactly three elements we provide a precise description of $$NA$$ for all $$N\geq 1$$.