Vibrant 4 Ply Aramid Reducer Coupling 1.75in Inlet x 1.25 Outlet x 3in Length - BlackVibrant 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; 1. 25 in. Inlet ID; 1. 75 in. Outlet ID; 3 in.