 It was made in five series, named with letters from A to E.
The series E introduced in 1914 showed the most significant revisions, so much that the model was renamed ALFA 20-30 HP.The ALFA 20-30 HP of 1914 and 1915, or ALFA 24 HP series E, was an update of the earlier 24 HP.The in-block camshaft was now chain- instead of gear-driven, the engine produced , and top speed was .