Our Brine 'Catch' Cup serves multiple functions. First, it acts like a weight in that it keeps the vegetables submerged under the surface of the brine. Second, it allows the maximum amount of brine to be added to the jar, eliminating as much oxygen as possible. Third, it provides a place for expanding liquid to have a place to pool, instead of spilling outside of the jar. Our Brine 'Catch' Cup is made of 18/8 Stainless Steel and does not react or interfere with fermentation as other metals do.