The ball lock keg I got is a Firestone Challenger VI. The gas in tube as shown is plastic and smaller diameter than a SS gas dip tube. I ended up finding a tutorial online showing how to drill out the gas in dip tube port to use the readily available SS gas dip tube. The port was 5/16" about 1/4" down then it reduced making a regular 5/16" SS tube not fit. It is now drilled out to accommodate the other style tube. The reason I wanted to replace it was the flange on the plastic tube is warped. Also the rebuild of rings sets don't fit snug around the plastic tube.