I don't know exactly, because I have it installed in my Safari Cab hardtop, which has more headroom than the factory hardtop, but here's a photo of a 2-gallon Rotopax on the panel in a factory hardtop. This photo is of a preproduction version of the overhead panel and there's about 1/2" of clearance above the container. The production version is supposed to be about 1/2" lower than this panel (notice how the bottom of the panel is higher than the bottom of the roll bar, I asked them to lower the panel so it's even with the bottom of the roll bar), so I'll estimate there's roughly 4" between the panel and the inside of the factory hardtop.