After the fastest delivery from Thomann I can remember (I ordered the Foam Net Pads as a replacement for my HD600s along HD650 cable and Headline Pad which I highly recommend), in less than a week I could easily substitute everything (Foam Net Pads included) with the help of some YT tutorials to avoid screwing up something.
The Foam Net Pads are good, thick and solid and they stand for quite some time, the only downfall I'd give them (probably I was unlucky and of course nothing lasts forever) on my HD600s stock ones they lasted less than 2 years, with the first one breaking a hole through and the second one tearing apart after 4 years in total.
They get very thin with time, but for the price I can assure they're good, not perfect but good enough to work.