The images I found that looked as if they'd interchange had no black bottom on the B22 carrier. I'd suggest waiting to order negative carriers until you have a C700 in hand. I should also note, however, that I've never used either of those models; that last enlarger I used other than my D2 was something or other in college, around 1978, and I don't even recall what brand it was (didn't care, it projected my negatives to a useful size and gave reasonable exposure times, and I was only shooting 35mm at the time).