Vibrant 4 Ply Reinforced Silicone Transition Connector - 3.5in I.D. x 4in I.D. x 3in long (BLACK)Vibrant Performance Aramid Reinforced Silicone Transition Hose Couplers feature a smooth and effective transition from one inlet diameter size to another. This coupler is intended for use in applications where a reduction or increase in diameter is needed. Our Transition Hose couplers are commonly found off of turbo compressor housings, intercooler end tanks and charge pipe assemblies. Reducer Coupler; 3. 5 in. Inlet ID; 4 in. Outlet ID; 3 in. Length;