Well I'm building boxes for my DC Tacoma. The bottom of the wedge will be 7.75" while the top is at 3.5". This is big enough to fit a sub with a 5.25" depth plus a .5" of ventilation space behind the pole piece. So I'd say you're probably looking at about 8.5 to 9" on the bottom, and 4 to 4.5" at the top.