Cusco designed this product to suppress the rising gear oil temperature by adding cooling fins and upping oil capacity (about 400cc). It aids in preventing LSD damage. Can be connected air-cooled oil cooler of M16 × P1.5 (sold separately). The installation of this product requires the following Subaru genuine parts. Air breather cap 38354AA020 × 1 Gasket (differential carrier) 38353AA050 × 1 Gasket (oil temperature sensor with def only) 803920050 × 2 (oil temperature sensor with def only) This Part Fits 2015-2017 Subaru STI Cusco Increased Capacity Rear Differential Cover