This is a push-fit 2 way t-connector used for connecting pole hose to jets on AR PRO water fed pole brushes.
What is push-fit? You can simply push the pole hose into the fitting and it will automatically lock in place. After, you can remove the hose by pressing the outer ring of the connector, which unlocks the hose.
All of the connector inserts are intended for a pole hose that has an 8mm outer diameter.