This is the charging adaptor for the HW100 cylinder. Please note newer guns may have the quick fill adaptor and so this adaptor will not be required.
Weihrauch HW100 Intermediate Fill Adaptor - Pre Quick Fill. Allows for fitting the detachable receiver to a 232 BAR DIN Female outlet. Can also be used for emptying the air receiver.
Remember, do not bleed the line or valve if using a dedicated gun charging system, as you will vent all of the air from the HW100 resevoir.
Simply close the cylinder valve, and unscrew the receiver from the adaptor, a small discharge of air is normal