For gas service that is "Clean For Oxygen Service (CFOS)" or for Ultra Pure service, manifolds and change over assemblies are typically made from 1/4" OD, 316 L, Electropolished tubing (the ID is Electropolished). The fittings used for ports and other connections are exclusively the "VCR" fitting. Training is needed to properly handle and install VCR connections using a variety of non-resuseable crushable metal gasket materials.