install and replace one wheel with another. The compressor housing has to be set up to specific tolerances for each specific wheel. Additionally, the wheel assembly (The compressor wheel is held onto the threaded turbine wheel shaft with a nut) has to be precisely balanced. I don't know what the difference is between the Garrett and HKS wheels, but I know that HKS uses Garrett parts for their turbos, so they may be fairly close in terms of performance. It's hard getting info from either company, as Garrett doesn't support a high performance department, and HKS is pretty tight lipped about their products. Maybe someone with more inside info than me can give you specific performance data. Take care, Mark