Carbonator cap made of stainless steel. Inject CO2 in use with product black ball lock connector/ coupler.
P.E.T. thread ( Easily thread on to soda pop plastic bottles, 2 ltr, 1 ltr, 16 oz. and 12 oz. size that typically use the same thread.)
1/4 internal barb- Allows connect to hose and carbonation stone.