 The standard GM2 reflector gunsight was introduced in mid-1939, although many Hurricanes retained the "bead".Fuel capacity was 97 Imperial gal (441 l) in two fuel tanks, each of 34.5 gal (157 l) in the wing centre-section, between the spars; the fuel was pumped from these into a reserve gravity-feed tank which held an additional 28 gal (127 l) in the forward fuselage, just ahead of the cockpit.This was the main fuel feed to the engine.