CGA 440 is a type of connection. All gases have a unique CGA connection. This is to prevent gas mix ups. For example, this prevents people from inadvertently connecting a nitrogen tank to a patient who needs oxygen, because the connections won’t allow the nitrogen to be connected. 

Hoses come in varying lengths. The inner diameter can vary as well. The industry standard is ½” I. D. and tens of thousands of these are sold each year.  However, some users prefer the ¾” I. D. transfer hose when filling from a bulk to truck tanks because liquid oxygen transfers faster with less boil off.