the 4x5 condensors are something like 6" in diameter.
maybe it is just the d3v's that have the extra condensor that slips in above the 4x5 condensors ... there is a diagram when you flip the door that says "this way" for 35mm, and "this way" for medium format ...
if i can dig mine up, i'll post a snapshot of it, just incase you need to know what to look for -