Both. It really depends on your setup. Manifold, WG placement, turbo placement and size. Sometimes you can get away with putting your Fan on the other side so its Pushing air through the radiator. Leaves you more space on the other side. Some manifolds have the external WG pokeing toward the radiator, so you need a Half size rad. Really depends on many factors. I was running a half size rad with slim fan pushing, but the stock full size rad would have fitted too.