I have a 55 baffled for a sump, the drain compartment is 14x14x14 ish (don't remember the exact measurements) the baffles are over under over and I spaced the so you can put rubble in between the under and final over baffles, the main compartment is sized like 24x14x14 ish big enough for the skimmer, return pump, probes, floats etc.