Today, Garrett turbo has a wider selection of turbochargers available than they ever have before! In the catalog, Garrett product are grouped by their frame size. The turbine frame size of a turbocharger center section or "CHRA" is dictated by its inducer diameter. The bigger the turbine inducer, the larger the frame size, so any garret gt or gtx turbocharger in the GT42 or GTX42 family has a bigger turbine inducer size than those in the GT35 or GTX35 family, and so on. The model name of each turbo or Center section (CHRA), you'll notice two digits directly after the frame size. These two digits designate the compressor exducer size in diameter, as measured in millimeters. Let's look at the GTX4294 as an example. The unit has a GTX42 frame size turbine (82 mm) coupled to a 94 mm (exducer dia) comp wheel. If there is an "R" on the end of it, then that means the unit is a ball bearing turbo. So, a GT4294 is not a ball bearing turbo; whereas a GT4294R is a Garrett ball bearing turbocharger. If an “X” appears between the “GT” and the first number, it signifies that this turbo features a billet compressor wheel with "next generation aerodynamics". The Garret GTX line is visually different in that the wheels typically are forged (billet), fully machined wheels rather than cast.