For a finite group G denote by N (G) the set of conjugacy class sizes of G. Recently the following question has been asked: Is it true that for each nonabelian finite simple group S and each n ∈ N, if the set of class sizes of a finite group G with trivial center is the same as the set of class sizes of the direct power S n , then G ≃ S n ? In this paper we approach an answer to this question by proving that A 6 × A 6 is uniquely determined by N (A 6 × A 6 ) among finite groups with trivial center.