There is 3 options available to purchase here however all are made with push fittings so can be swapped around to any combination easily.
Liquid to Liquid (use for transferring liquid from one keg or pressure fermenter to another, then disconnecting to use a tap)
Liquid to Gas (attach to the liquid out post of a large keg and the gas in post of another keg with a tap on it's liquid out post. Attach the regulator to the large keg and the one with the tap will always be full and ready to remove from the system for a portable option.
Gas to Gas (attach the gas posts of 2 vessels together briefly to equalise the pressure between them ready to transfer liquid from one to the other)