The key caps are made by Cherry, and have Cherry's profile. They are as thick as the double-shot keys, but made from a plastic called POM instead of ABS. As I understand it, the Das Keyboard II is the same as Cherry's contemporary black G80-3000 keyboard with clicky switches, just without the legends.
Personally, I am not a fan of Cherry's POM keys because POM plastic feels more slippery than ABS or PBT.