A typical Bilstein front strut:
Note that the shock piston actually travels with the suspension and the body of the shock remains fixed
to the vehicle. This greatly reduces unsprung weight.
It also allows the larger surface area of the shock body
to act as the lateral structual member making the
strut assembly stronger, reducing wear, and promoting
longevity. The shock oil is also exposed to open air
allowing fast dissipation of heat, reducing wear and increasing longevity.

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