Mine were Grohe. I ordered the replacement cartridges through faucets.com or something like that. There is a left and right.
I was, like others, just going to replace them with something from HD, until I took mine apart and saw how robust the construction was and how good the chroming was and after finding out how much Grohes were, I decided that spending as much for cartridges as a HD replacement unit was money well spent.
BTW, if you find that is what you have, you can PM me for the part numbers. I think I have them at home, altho I won't be leaving the island until Tuesday.