Phat Phat Filter 39"x12", 1700 CFMProduct Details Phat Filters are packed full with the very best carbon on the market and we have the independent lab test numbers to prove it. How do we know? Simple math. Carbon Quantity x Carbon Quality = Filter Capacity QUANTITY: When we say Phat Filter carbon beds are 2" thick, they are in fact, 2" thick. The same is true when it comes to Phat Filter bed length size; the size we claim is in fact the actual size, not a rounded up dimension to make