Probably got the wrong part. I got some off eBay that work fine, ~$25 for two. They don't have the star imprint, but they have the part# and are likely produced by an OE supplier. You can also take them apart if you're good and clean them out. The rocker plastic broke on the originals in my car or I would have done just that. Never heard of Truck Tech, & why would anyone buy a part for a Mercedes from such a place?

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'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)