Let \(\sigma = \{ {\sigma }_{i} \mid i \in I \}\) be a partition of the set of all primes. A set \(\Sigma = \{H_1, \ldots , H_k\}\) of \(\sigma _i\) -Hall subgroups of G is said to be a complete Hall set of type \(\sigma \) of G if \((|H_i|, |H_j|) = 1\) for all \(i \ne j\) and \(\pi (G) = \pi (H_1) \cup \cdots \cup \pi (H_k)\) . A \(\sigma \) -subnormality criterion is proved in terms of products of subgroups of a complete Hall set of type \(\sigma \) .