These are the same adapters you see at every growler fill station. Now you can show up with your own, and get them to fill your keg directly without ever being exposed to oxygen.
If you already have a Mini Keg and a Pro Tap Kit but you want to bringthe freshness of your beer to the ultimate level, here is the way.
A regular growler will only keep beer fresh for a few days. The Pro Tap Kit will keep it fresh for weeks, which plenty for most people. But if you really want to make it last you need to make sure it never comes in contact with oxygen.
Here is how:
Simply attach the Picnic Tap Kit that came with your Pro Tap Kit to your keg but replace the tap end with the Growler Fill Adapter. (as seen below)
At the fill station insert the filler right inside the tap. (most fill stations will have sanitizer on hand to dip the filler into before inserting)