No idea. I just made it as big as I could given the space limitations of the cubbyhole. I'm guessing it's about 3-3.5 litres In theory it shouldn't work, which is why I'm always slightly skeptical of HiFi theory when it comes to in car systems. The enclosure is too small, the JL sub itself is only rated at 75wrms yet I put 200-300wrms through it and it takes it (with a bit of care). But the transformation of the upgrade is awesome. I feel if I made the same enclosure from fibreglass it just wouldn't work. I'm old skool I'm afraid & Bass & plastic enclosures just don't mix.