The APR Turbo Inlet System is a comprehensive upgrade to your factory or modified intake system. To maximize performance addressing the restrictive components between the airbox and turbocharger are a top priority. It's common to individually upgrade these components, but doing so is not ideal as it mean sacrificing overall design for the sake of compatibility. This is why the APR system is one complete upgrade from the turbocharger to the intake airbox. We were able to increase the diameter as large as possible with the best geometry from the turbo to the intake airbox to promote the maximum amount of flow with the lowest pressure drop. The system starts at 80mm and can expand up to 88mm for larger airbox systems. For any given size inlet there is a theoretical maximum flow limit, but in real world testing the actual results are typically around 90%. On the GTI we set out to achieve this limit and hit 90% of the ideal maximum with the APR turbo inlet! This means the turbo doesn't have to work as hard, which translates to lower temperature, and improved performance. This system is compatible with the factory intake airbox, and works perfectly with an APR intake filter for those who prefer a "stealth" OE airbox upgrade. It also pairs perfectly with our myriad of intake airbox only intake systems, such as the APR Carbon Fiber and PEX open systems. Of course, none of these systems compared to the performance potential of the complete APR intake system with modular covers, but the performance is the best you can expect without upgrading all 3 components in one design (turbo inlet elbow, turbo inlet pipe, and airbox). Every aspect of the system has been perfected for performance minded individuals. The hose is wire reinforced so there's no chance it will collapse under heavy load and heat. Since oils from the PCV will eventually work their way into the system, we line the hose with fluorosilicone ensure it's oil and fuel resistant. And lastly the turbo inlet adapter is removable, giving you the flexibility to grow with this system as you see fit!