They are different rates. By 'rate' I mean stiffer or softer. The spring on the left (long and thin) is a softer spring. The one on the right (short and fat) is a stiffer spring. You would chose a spring depending on whether you want comfort or performance or light or heavy loads.
The ad leads you to believe the springs are a replacement for a particular spring...they aren't. It's only the spring manufacturers recommendation. The different PSA (Citroen) part numbers will represent different rates of springs (they may also represent different manufacturer of the same spring rate...confusing). So its not possible to replace a number of spring RATES with just one.
What the ad is saying is these springs will 'fit' where any of those part numbers would be used but they only do two springs, stiff and soft, so they 'recommend' those springs replace those part numbers.
It looks like 5002.LK is right in the middle of hard and soft, so they recommend either springs.
The ONLY way to GUARANTEE you get exactly the right spring is to go to Citroen.
If you don't care that it's exactly the right spring, chose hard or soft, buy two, fit them to your car and move on.
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