I just got a pair of these spare cushions for my ca 15 years old DT-150s. The old cushions were cracked and the foam inside them were showing, so not a pretty sight and not too comfortable to wear. The replacement pads make my headphones look and feel new again. In this age of wear and tear I can only praise Beyer for offering spare parts like these.
The pads don't come with any instructions on how to remove the old an fit the new. It is a bit fiddley, and I found a diy on Youtube for the DT-100s that was helpful.
All in all, this is a fairly easy way to give new life to old phones. I love it.