A constrained geometry catalyst (CGC) precursor, Me(2)Si(Flu)(N-t-Bu)ZrX(2) (X = Cl or NMe(2)), behaved as a single site catalyst with methylaluminoxane (MAO) as cocatalyst, while it developed much diversified catalytic species with AlR(3)/Ph(3)CB(C6F5)(4) as cocatalyst. The catalytic performance was not affected if X is Cl or NMe(2).