As I recall, when you buy a Silca (I'm old but not that old, I just started young), you tell the bike shop "my frame is a 52cm" and the Silca pump, for example, will be 49-53 lets say. The head (I'm going from hazy memory) is part of the measurement. In other words, if your frame is 52cm and the pump is 52-56 cm, putting a campy head on it will probably fit cause that's part of the measurement. If it is too big, you can always put it under the top tube.