Retaining ring for tube size 1/2" bulkhead unions feature a unique design that provides the user with an economical method to install and assemble a union connection through a bulkhead. The retaining ring bulkhead unions feature a smaller envelope size than standard bulkhead union connectors and do not require a wrench to mount or assemble in cramped areas. The external seal feature provides a moisture barrier and can also prevent external contamination from entering into an enclosed area. To install, simply support the bulkhead union from behind and apply the external seal. Then push the external retainer against the external seal with an assembly tool and you have a reliable bulkhead connection in a confined area.