https://www.youtube.com/watch?v=jebpq5KTgz4 Lads these are just great cheap bits of kit. If you pressure transfer beer from Fermenter to Corney then you can adapt this to be an inline sight glass using a clear bottle so as to view the beer on the way to the Corney. You can also use it to make up clearing agent and force co2 it through the gas post into the keg, no air. You can fill a plastic bottle with beer under pressure. You can fill a bottle with Tap cleaning gunk and flush your beer taps.
https://www.youtube.com/watch?v=KWTCP6Cb6V0&t=83s This lad using it too