The CSF radiator is different than your typical aluminum high performance racing radiator. The tube design is called a B-Tube. The B-Tube does not use rows of tubes like an old school radiator but instead has a series of long stacked thinwalled plates much like a tube and fin intercooler. The B part of the tube refers to an internal rib in the middle of the plate which both strengthens the wide plate and helps exchange heat to the outside of it better. The B tube exchanges heat 15% more effectively than the traditional rows of oval shaped tubes.
The FR-S/BRZ radiator uses this external cap adaptor so a standard SAE cap can be used. This gives the user a choice of a wide variety of high pressure racing caps made for domestic cars for low prices.
The CSF radiator comes with this 20 psi cap, but higher pressure caps can be used as well.
A strong machined aluminum drain plug is used. Made of all TIG welded construction, CSF also has a 40% higher burst strength than the stock radiator with it's crimped on plastic tanks. Finally the radiator end tanks are hand polished for nice looks!
Made from aircraft aluminum welded to the end tanks, the radiator core itself is >32mm thick vs the stock 15mm which is more than twice the thickness! Typically a good heat exchanger design is less that 1.5″ thick for best efficiency and the CSF falls right into this range.