These ball lock posts would enable you to make a keg out of any pressure vessel if you wanted to.
These ball lock posts include a 1/4 inch BSP thread so you can attach it to a wide range of other fittings. The posts include a 20mm long thread, an o-ring, poppet, locking nut and short dip tube.
Please note the Liquid post does not have the score around the edge. The score around the edge is for gas. Have a look at the photos if you are confused.