Small brass part that fits into the CO2 Cylinder valves preventing contamination getting into the gas cylinder. Can be removed with 5mm allen key.

This is a replacement part that fits inside the KL01502.

The RPV (residual pressure valve) is a small valve that fits inside the CO2 gas cylinder and keeps a small amount of positive pressure inside the cylinder once the cylinder has been emptied.  This positive pressure inside the gas cylinder prevents contamination getting into the cylinder and it's one of the reasons why cylinders fitted with this type of valve only require hydro testing every 10 years.

These RPV valves may sometimes need to be replaced over time.  For instance if they do not hold any residual pressure in the cylinder or of they hold too much pressure then the RPV will need to be replaced.

When an RPV valve is operating correctly it should hold more than 1 bar in the cylinder and less than 5bar.