Abstract: A configurable port fitting for a container, such as a bioprocess bag, has one or more O-ring grooves and two opposing locking arms (e.g., 604). The port fitting is mounted onto the container by (i) inserting one end of the port fitting into a port in the container such that O-ring(s) form seals between the O-ring grooves and the container and (ii) rotating the port fitting to engage the locking arms with two opposing retention clips (e.g., 506) of the container. Some port fittings are fixed port fittings that provide a fixed opening into the container. Other port fittings are port sizers that receive a valve connector that enables flow control between closed and open positions. Port fittings of different sizes enable different flow rates. Some port fittings (and other connectors) have a threaded tube barb that receives a threaded tube retainer that secures tubing in place over the barb.