There is absolutely no difference in size between the two boxes. The 6 holes vs. 3 holes I've been mentioning are in the plastic just behind the filter screen. The outside three holes (tubes) on the top are the same for both boxes. I have four of these air boxes (two of each) and all are slightly different in design. On some, the part I've described is integrated into the box molding. On others, it is a removable piece. The only difference is in the number of internal holes. No more air gets into the box since the outside holes are the same. The difference is that the air inside the box is freer flowing and probably enters the box faster. The other major difference in the carbs is that the Ciao is a 10 mm carb (dellorto 12.10) and the Grande is a 12 mm (dellorto 12.12). On the 12.10, the brass fuel tube has two small holes in it, on the 12.12, there is one larger one. I hope this description is clear. If not, I could probably scan the six hole version and post it.