The hexagon screw head is machined much higher so they are easier to grip with your fingers.
The hex uses the same standard 8mm across flats for the 5mm threaded screw and also has a flat cut in it for a screw driver to be used. made by MB.
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Dellorto PHBL and PHBH carb top easy screw, made in stainless steel. The hexagon screw head is machined...
MB Dellorto O ring and float set, to protect your carburettor from the ethanol that is in modern fuels....