reserve U for Universe;
reserve x for Element of U;
reserve U1,U2 for Universe;

theorem
  for C,D being U-small Category holds Functors(C,D) is U-small &
  NatTrans(C,D) is U-set
  proof
    let C,D be U-small Category;
    thus Functors(C,D) is U-small by Th72;
    then the carrier' of Functors(C,D) in U;
    hence NatTrans(C,D) is U-set by NATTRA_1:def 17;
  end;
