The M3 was protected by 51mm frontal armor, sloping at an angle between 45 to 53 degrees. The sides of the hull were 38 mm thick and sloped at an angle of 90 degrees. The hull was cast, riveted and partly welded. The M3’s cast turret was 51 mm thick. The tank was accessed through two large hatches located in the side walls of the hull. The M3’s armament consisted of a 75 mm main gun in the right front side of the hull. The gun could traverse within 30 degree angle, which was a major disadvantage as the tank had to turn in order to engage enemy. In the turret, there was a 37 mm gun along with a Browning .30 (7.62 mm) calibre machine gun. The tank was manned by a crew of six: a driver, wireless operator, two 75 mm gunners, one 37 mm gunner, and the commander in a dome, initially located on top of the turret, armed with a 7.62 mm machine gun. British did not like the silhouette of the M3, therefore they removed the dome and renamed the tank M3 Grant. The original tank version, which went into service in the US army, was named M3 Lee.