Factory-Original SU piston spring.
This is the "Red" version with a load at length of 4.5 oz. @ 2.635 in.
It is recognizable by the red paint on one of the ends (see photo).
These springs generate a resistance which balances the venturi size with the correct air flow and mixture.
Consequently, this spring is considered an important "tuning part" so choose yours wisely.
This product is priced, and sold, as a single unit.
Required quantity per carburetor: 1
This is an original SU spring, Made in the UK!
This is SU part number: AUC4387 / AUC 4387