System1 Designs 4" to 3" Inch Silicone Black Coupler 3 Layers of Polyester Reinforcement Suitable High Level Straight Reducer Intercooler Hose Intake Piping System1 Designs line of silicone couplers feature 3 layers of polyester reinforcement and are suitable for applications with boost pressures up to 45psi. They also feature a temperature rating of 428°F for direct to turbocharger installations. Features: System1 Designs line of silicone couplers feature 3 layers of polyester reinforcement and are suitable for applications with boost pressures up to 45psi. Size: 4" to 3" Leg Length: 3.5" Material: 3-ply Polyester Reinforced Temp: 428 Degrees F (220 C)