Let n be an integer and B n be the variety defined by the law [x n , y][x, y n ] −1 = 1. Let B * n be the class of groups in which for any infinite subsets X, Y there exist x ∈ X and y ∈ Y such that [x n , y][x, y n ] −1 = 1. For n ∈ {±2, 3} we prove that B * n = B n ∪ F, F being the class of finite groups. Also for n ∈ {−3, 4} and an infinite group G which has finitely many elements of order 2 or 3 we prove that G ∈ B * n if and only if G ∈ B n .