The PRE+28 Connector is the pre-filter to your MUV system. It allows you to connect the Hose Adapter or a soda/water bottle to your filter. It comes with a rubber end cap to keep your filter safe while in transit, a plastic strainer to keep large debris out of your filter, and a pre-filter felt which keeps smaller particulate out of your filter.
The PRE+28 Connector has male connection points and is always attached the bottom, female end, of the MUV water filters.