procedure TfrmMain.FormResize(Sender: TObject);
var
  i: integer;
begin
  FlowLayout1.BeginUpdate;
  for I := 0 to FlowLayout1.ComponentCount -1 do
  begin
    if Components[i] is TRectangle then
    begin
      TRectangle(Components[i]).BeginUpdate;
      TRectangle(Components[i]).Width := (FlowLayout1.Width / 3) -10;
      TRectangle(Components[i]).EndUpdate;
    end;
  end;
  FlowLayout1.EndUpdate;
end;