This cap fits over the barb outlet on regulators and VIPR cylinders.  These caps/covers have a small hole in the end to allow for small weepage of gas to escape without pushing the cover off of the hose barb.  We sell DISS Connection Caps to match the red and green hose barb covers.  We also have patented hose barb caps which are designed with ribs to prevent the user from installing a nasal cannula over the hose barb cover without first removing it.  It is also vented to allow for small amounts of oxygen to weep out without building up pressure and forcing the barb cover off.  We have hose barb covers available in three different colors.  Green - ACM 446;  Red - ACM 416; and Black - ACM 204.