The carburetor preheat duct is a multi-purpose air ducts, it is made by 3 or more layer materials. 

This Preheat duct is designed for connection between engine exhaust manifold and the air cleaner as a carburetor preheat duct. In addition, this durable, flexible, multi-purpose air duct can be used in vehicle cabin ventilation as an air or defroster hose, or an emission control hose.

Raw materials: Aluminum, stainless steel, glass fiber, pvc, kraft paper, insulation wool
Length: 50mm to 15m.
Installation: Can be installed with or without worm gear clamps. Cut to size with long-bladed knife

Hot sell structure of carburetor preheat duct
aluminium+fiberglass+aluminium
aluminium+aluminium+fiberglass
PVC+kraft+aluminium

paper+aluminium+paper