The lighter weight blue spring was rarely used as standard on
HS2 single and twin carbs but the heavier red spring
AUC4387 was. Noticable excetions to this where they fitted this spring are- Mini Cooper 997/8 1964-69
ADO16 2and 4 door twin carb Wolseley and Riley 1300- 1300GT
early Sprite and Midgets until 1972 when they changed to red