I've used these to replace the tired old vinyl ear pads on my (now rather old) DT100s. I use them in a project studio environment, mainly for tracking vocals etc. in an isolation booth.
These are fairly easy to swap for the stock vinyl pads that come with a pair of DT100s, and once you've wrestled them in to place are unlikely to come off without you wanting them too.
The finish is, as described, velour. This is (subjectively) more comfortable on the head, although those with stubbly beards might find the stubble on velour a little 'velcro'-ish.
One might expect that the seal between head and pad to be slightly less sealed than the stock pads, but I haven't noticed any more pronounced headphone spill.
I have found these to make my head sweat far less than the vinyl pads, and after prolonged use in a (warm) vocal booth, that's something that matters. This seems an improvement, but on the flip side there's a nagging suspicion that these are less hygenic and that sweaty singers that have visited have left their sweat on my velour, rather than being able to wipe clean (like the vinyl ones).
Overall these pads are fine, and offer a slightly more classy feel than the original pads. This comes with the caveat that I am not actually sure that it's an improvement. I certainly wouldn't pimp my DT100s straight out the gate with them, I'd wait until new pads were needed, then choose whether these are what you want to replace them with.