GCG Custom Turbochargers live under the "XTR" name, which is an abbreviation for Xtreme Turbo Racing. The XTR branded turbochargers are usually Garrett units, that are modified to flow more, or perform more efficiently in a particular application. It is also applied to turbochargers which may have custom housings, which are modified and fitted to suit a customer's particular application. A good example of a true GCG built "XTR" branded turbocharger, is the GT3566R-SPL2. This turbocharger is built with an 0.80a/r Compressor Housing, and a 66mm Compressor Wheel which is mated with the standard GT35R turbine wheel and turbine housing.  This is a combination which Garrett do not offer as an off the shelf unit, but as its a combination that works in many applications, it is offered as a custom built XTR unit.