my boxes are each .75 cubic feet,, according to jl reps which i talked to it gives you the most accurate bass,, and thats .75 with already taking into account space taken up by the sub and sealent and everything. most subs come with good directions about how to go about building your own box. i even had a light stuffing added to my boxes recently. something i learned from the kicker websight which actually does give it a deeper bass feeling.