The original OE oil cooler from BMW is an all metal design which would make you think it would be fairly robust. However, there are several weak spots in the design that tend to cause leaks. The CSF Race-Spec design reinforces the weak points, especially around the feed and return lines. CSF's solid line connection block can handle any abuse thrown at it while the reinforced and braced return tube is rock solid. CSF also upgraded the more fragile Tub/Fin core to a robust and durable Bar/Plate design. The core is 40% larger than the factory unit with 2 additional rows of oil cooling and much thicker core (63mm vs OE 45mm). This offers superior cooling capacity and volume for the oil system. TIG welded end tanks round out the slew of upgrades creating a much stronger connection than the factory brazed construction.