This cover is spreading dust itself. It's elastic, and underneath the cover its losing very fine black powder, dropping on the keys. I've seen this happen with old elastic fabric, but never with something so new.
The tag on the product says that according to Californian regulation, the product is carcinogenic. You'll understand I would never have bought this product if I had known in advance. Alas, I unpacked it rather late and it was too late to return with the fine returnpolicy that Thomann uses.
However, I strongly advice against buying this. I'm not sure if the dust it spreads is carcogenic too, but I'd rather not find out. And even if it's not, what good does a dustcover do that adds to the dust on your keys?
The fit is great and a bit adjustable, but I will never buy elastic material again. Oh, and I did test with half the keyboard covered for a week, to see if it was dust from the room going through the cover somehow. It wasn't: on the uncovered part there was just a bit of normal grey dust after a week, under the cover there was more of the fine black powder again.
I can't imagine it's good for your keys, nor your lungs.