Here's amazing value in this four piece cap assembly. A polished alloy, hinged cap (dimensions 100mm x 134mm) screws on to an anodised alloy, threaded neck with an integral, 51mm dia, filler hose connector.
A lockable non vented insert fits in the neck and a separate threaded slip ring with cork gasket allows you to 'sandwich' your flat body panel between the cap and the neck. Fits into a 76mm (3") hole. Very neat. Weight 740 gms.
ASTON CAP ASSEMBLY #AST100