For Honda Civic Si 2.0L 3-Ply Silicone Radiator Coolant Hose (Red) - 7th Gen EP3 K20 3-Ply (4mm) Nylon for Strong Reinforcement Increases Engine Performance and Efficiency and Helps to Keep Engine Bay Temperatures Cooler Withstands Operating Temperatures up to 330F Degrees Fahrenheit Main Hose Inlet/Outlet Inner Diameter: 1.125"/1.125" / Size (Diameter) Tolerance: +/- 0.225" Work With Factory or Aftermarket Radiators