Lab Glass 5000ml Buchner Funnel Apparatus, Filting Funnel Kit for Vacuum Suction Filter

I purchased two of these sets. They arrived in good shape. The 5 liter flasks are outstanding. The Buchner funnels are next to worthless. They are clearly of pour quality. One has hairline cracks which are soaking up the mixture poured into the funnel for filtering. Worse yet is the fact that the perforated surface where the filter is placed is not flat. In fact it is convex (domed) and the filter can't lay flat. When wet with the solution to be filtered the filter wrinkles as it curves around the dome therefore leaking unfiltered fluid past it contaminating the filtered solution in the flask.