Considered the most effective variant, the Model 52 was developed to face the powerful American Hellcat and Corsair, superior mostly for engine power and armament.The variant was a modest update of the A6M3 Model 22, with non-folding wing tips and thicker wing skinning to permit faster diving speeds, plus an improved exhaust system. The latter used four ejector exhaust stacks, providing an increment of thrust, projecting along each side of the forward fuselage. The new exhaust system required modified "notched" cowl flaps and small rectangular plates which were riveted to the fuselage, just aft of the exhausts. Two smaller exhaust stacks exited via small cowling flaps immediately forward of and just below each of the wing leading edges. The improved roll-rate of the clipped-wing A6M3 was now built in.

The A6M5 had a maximum speed of 540 km/h (340 mph) and reach a height of 8,000 m (26,250 ft) in nine minutes, 57 seconds. Other variants were the night fighter A6M5d-S (modified for night combat, armed with one 20 mm Type 99 cannon, inclined back to the pilot's cockpit) and A6M5-K "Zero-Reisen"(model l22) tandem trainer version, also manufactured by Mitsubishi.                                                                                                                                          -- Wikipedia