This really handy device is great for filling kegs, keg to keg transfers or fermenter to keg transfers.
 
Fantastic for use with Fermentasaurus or other pressurisable fermenters.
 
Simply attach this device to the output gas post of your Keg then when the keg is full it will prevent further liquid exiting the gas post. This means you can literally set and forget and fill kegs automatically without the risk of kegs overflowing all over the floor.