This is a 3/8" by 1/4" by 3/8" reducing tee with quick connect fittings. No tools necessary to connect tubing. Simply push tubing fully into the ports. To release the tubing, push collet flush against the plastic body and pull tube out. Commonly used when connecting a reverse osmosis drinking water system to a refrigerator. Please see the instructions on how to connect and disconnect John Guest fittings and connectors.