They're easy...The coco/coir fibers don't seem to absorb anything at all, rather, dirt falls through the weave and onto the rubber base. Holding upright, I smack them a few times with the palm of my hand and any dirt that's settled beneath the fiber falls right out. For dust or other small particles, I hose em down and dry them upside down. They're silly expensive but well worth it...

And one thing I never read here while researching whether or not to buy was how much highway sound they end up damping -a significant amount.

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1981 240D 4sp manual. Ivory White.