A total of 237 Re 2001's were eventually delivered to the Regia Aeronautica, these being powered for the most part by a license-built version of the DB 601A, the Alfa Romeo RA 1000 RC 41-1a Monsonie (Monsoon) rated at 1,175 hp for takeoff. Armament of the initial version comprised two fuselage-mounted 0.50 in (12.7 mm) SAFAT machineguns and two wing-mounted 0.303 in (7.7 mm) SAFAT machineguns.
Variants included the Re 2001 C.N. (Caccia Notturno, Night Fighters), with 0.787 in (20 mm) MG 151 cannon replacing the wing-mounted 0.303 in (7.7 mm) weapons, and the Re 2001 C.B. (Caccia Bombardiere, Fighter Bomber) with provision for a single 551 lb (250 kg) bomb. Known as the Re 2001 Delta, one example was fitted with an Isotta-Fraschini Delta RC 16/48 twelve-cylinder air-cooled inverted V-engine rated at 840 hp at 17,390 ft (5,300 m).
Converted from the Re 2000 prototype, MM408 became an additional Re 2001 prototype. As described by Carlo Soliani, it appeared in three configurations:
1st: natural aluminum finish transparent pilot headrest fairing
2nd: green & brown camouflage finish transparent pilot headrest fairing
3rd: green only camouflage finish modified pilot headrest fairing (solid)
During WW II it was a common practice among the Italian aircraft manufacturers and military forces to release official photographs more or less retouched. Retouched photo 1784, taken at the same spot at the same day, shows the retractable tail wheel doors deleted and an antenna added, as became standard at production models. Compare photo 1784 with an unretouched copy (apart from the background) of the same photo supplied by in this composition.
Span: 36 ft 1.1 in (11.00 m)
Length: 27 ft 5.1 in (8.36 m)
Height: 10 ft 4.0 in (3.15 m)
Wing area: 219.58 sq.ft (20.40 sq.m)
Weight empty: 5,423 lb (2,460 kg)
Loaded weight: 7,231 lb (3,280 kg)
Max speed: 339 mph (545 kmh) at 17,945 ft (5,470 m)
Climb: to 16,405 ft (5,000 m) 6 min 20 sec
Range: 684 mls (1,100 km)."