There are two different kinds of chamber systems out there; plastic and concrete. The concrete chambers are usually 4'x8' or you can get 4'x12'. They are placed in rectangular designs and are primarily used under driveways or parking lots as they have the strength to support such a load. The bottoms of concrete chambers are open and they have holes along the sides for effluent to flow out of. The plastic chambers are a bit smaller in size and a person can easily pick up several of them. They are about 1.5' wide and 4.5' long. They are usually placed rather close to each other and are a bit more flexible in their arrangment than concrete chambers. The bottom of platic chambers is open and instead of holes in the side of these chambers the sides have louvers in them that go about 10" up the side of the chamber.