Impreza WRX STi (GC8 - except Type R/RA) and Impreza WRX (GD) with R180 differential conversion 500HP Rear Axles (R180 Differential ONLY). These axles use our new proprietary outer CV that is a direct fit to the factory wheel hub, our aerospace grade torsional 32 spline axle bars, increased from the factory 29 spline bars, and a billet ball & cage inner cv with our high grade inner differential spline for the R180 differential.