The diameter of the front suspension strut must be determined for the clear indentification of the required suspension of all VW Golf 5 to Golf 7 as well all derivatives of the manufacturers Audi, Seat and Skoda.
There are two different version with 55 and 50mm diameter.
You have to measure this diameter at the original shock absorber at the mount where the damper is clamped in the wheel bearing housing.
You can take a closer look on theese two pictures

