Air-Arms Filling Probe (later T bar)
New Style Air Arms Female Fill Adaptor.
Suits the Air Arms S400/410/200 and the new S510.
This is the hose end fitting with 'T' bar slot to locate on the new style fill valve with the 'T' bar retainer on the end.
Also fits early 'New Style' valves without the 'T' bar on the end of the fill valve. (Quite rare)