Hydro lifter made by a reputable German OE manufacturer.
A worn hydro lifter can be identified by a loud rattling noise right after engine start. The frequency changes with rpm.
Once oil pressure has been built up the noise may disappear. But it'll get worse and some day it won't disappear anymore.
A defective hydro lifter causes excessive valve play. This again causes serious loss of engine power because the corresponding valve will not fully open anymore.
