The dampers are made under partnership with Sachs and another company. Sachs provides the materials and mfg, and Eibach does the development and testing to spec the valving.
I've read good reviews on this kit for VW's in "European Car." The authors did not address longevity, though, and we've heard that Sachs is less than stellar in this area. The valving is probably dead on, and the price must not be too bad, but I suppose you'd really have to weigh these factors against Sachs' involvement in the product.
