The 50mm hose fitting adaptor HN64CF (SA) is a fitting designed for the use by the South Australian country fire authority tankers. These are essential for any designated fire storage tanks.
The real benefit is the tanker operators know the fitting on the tank will be easily and quickly connected to their hoses.
If you have tanks that are not designated fire tanks it maybe worth considering the addition of these fittings as they may be useful during a fire emergency.