On many pin & sleeve devices, an additional sealing ring must be tightened in order to ensure the achievement of rated watertightness. Users frequently fail to take this extra step, resulting in leakage.
Most MELTRIC devices have a “foolproof” design that eliminates the sealing ring. Most models achieve their environmental ratings simply by mating the plug with the receptacle. After the removal of the plug, rated watertightness is maintained for the receptacle by simply closing the lid.