Holset 57mm compressor wheel with inverse splitter blade, compressor cover and bearing housing. Uses an upgraded 76x60 10 blade turbine in a 12cm exhaust housing.
57mm is good for 425 horsepower at the tire
56mm is good for 380 hp at the tire. 56mm is perfect for a stock replacement on a stock truck. Whereas the 57 is good for a little added fuel or timing.