Alfa Romeo 2016 4C Spider Owner's Manual page 284

282 MAINTAINING YOUR VEHICLE
4. Leaving the plug close to the opening, put a finger on
the central hole in the plug and remove it: the level can
be seen on the control pipe due to capillarity.
Washer Solvent Plug
Washer Solvent Dip Stick
5. After the check, reinsert the plug with the control pipe
in the initial position.
6. Reposition the washer solvent protection panel and
tighten the four self-tapping screws.