Holset Turbo Specs There seems to be a lot of miss information on this topic, so I'm going to help clear it up some. First off what do the numbers mean, for instance a 56/60/12? The First number is the Diameter of the Compressor Inducer in Millimeters, in this case it's a 56mm compressor wheel. The Second number is the Diameter of the Turbine Exducer in Millimeters, in this case it's a 60mm turbine wheel. The Third number is the exhaust housing size in cm2, I'm not going to go into this, but generally speaking, bigger equates to laggier down low, but more power up top. There can also be Letters at the end like 'W', that gives us more information about the Turbine housing. 'W' Stands for wastegated. 'D' Stands for Devided. With that newfound information, lets get started. WH1C (56/60/12WD) The WH1C is found on 94 and some 95 Cummins, it is basically identical to the HX35 except it has a V-Band Compressor housing. The Turbine housing is a 12CM housing, is divided and has an internal wastegate. HX35 - 8 blade (56/60/12WD) The 8-blade HX35 is found on 95-98 12 Valve Cummins.  You can normally tell them apart because the wastegate canister is mounted on the turbine housing, where as the 7-blade's wastegate canisters mounts on the compressor housing. The Compressor is a 8 Blade 56/82 wheel.  Due to the larger exducer, this wheel is not interchangeable with the 7-blade design.  The Turbine is a 12 Blade 60/70 wheel The Turbine wheel has the older 'straight blade' design, they spool faster but don't flow as well. The Turbine housing is a 12CM housing, is divided and has an internal wastegate.   HX35 - 7 blade (56/60/12WD) The 7-blade HX35 is found on 98.5-02 24 Valve Cummins.  You can normally tell them apart because the wastegate canister is mounted on the compressor housing, where as the 8-blade's wastegate canisters mounts on the turbine housing. The Compressor is a 7 Blade 56/76.5 wheel.    Due to the smaller exducer, this wheel is not interchangeable with the 8-blade design.   The Turbine is a 12 Blade 60/70 wheel The Turbine wheel has the older 'straight blade' design, they spool faster but don't flow as well. The Turbine housing is a 12CM housing, is divided and has an internal wastegate.   HY35 (54/58/9W) The HY35 is found on '00-02 24 Valve Cummins with an Automatic Transmission. The Compressor is a 7 Blade 54/76.5 wheel The Turbine is a 12 blade 58/65.5 wheel The Turbine wheel has the newer 'curved blade' design, they flow better, but don't spool quite as fast. The Turbine housing is a 9CM housing, is undivided and has an internal wastegate.   HE341 (56/58/9W) The HE341 is found on '03-04 24 Valve Cummins. Most HE341 Compressors are a 7 Blade 56/76.5 wheel.  Very few have the smaller HY35 54/76.5 wheel.  The Turbine is a 12 blade 58/65.5 wheel The Turbine wheel has the newer 'curved blade' design, they flow better, but don't spool quite as fast. The Turbine housing is a 9CM housing, is undivided and has an internal wastegate.   HE351 (60/58/9W) The HE351 is found on 04.5-07 5.9L 24 Valve Cummins. The Compressor is a 7 Blade 60/84.5 wheel The Turbine is a 12 blade 58/65.5 wheel The Turbine wheel has the newer 'curved blade' design, they flow better, but don't spool quite as fast. The Turbine housing is a 9CM housing, is undivided and has an internal wastegate.   This is from Borg Warner's Website.