In this case, you have a combination of factors, first your electric box, which usually is recommended cutting 3 inches, and secondly your light fixture or ceiling fan canopy diameter. Both factors should be considered before choosing hole size, as you need room for all your wiring and hanging parts, and at the same time this hole should be covered by your canopy, also view product attribute to see what is this ceiling medallion canopy fitting specification. Please keep in mind the ceiling medallions with center hole cut are not returnable, because they are not resalable.