Make a really small and useful keg system out of PET plastic bottles. Great for taking beer to a party or making your own micro/portable/mini keg system.
Note: This is for the tee piece only. You need to provide your own soda bottle, carbonation caps and dip tube.
PET bottles are readily available and inexpensive. The standard thread for PET bottles for carbonated beverages between 0-3L in size is the PCO1881 thread.