Buchner Funnel:
A Buchner funnel is either a one piece porcelain filter apparatus, or a two piece plastic filter and funnel assembly. The filter part of the Buchner funnel has holes and requires it to be fit with filter paper.
It is important to wet the filter paper prior to filtering a solution to prevent the filter paper from floating on the solution and allowing particulates to pass through the funnel into the solution.
The green rubber stopper on the bottom is used to help fit the funnel to mouth of a filter flask for a tight fit.