Proflow Billet Aluminium Radiator Filler Neck Weld On, 40mm, Suit Normal Size Radiator Cap, Each - PFE462-02Part Number: PFE462 02 These billet weld on fill necks are ideal for use wherever a heavy duty, custom application filler neck is required. They feature a billet aluminium construction for durability in racing or street applications. These fill necks include barbed fittings for the plumbing of an expansion tank. Suit a 508 13 Radiator caps and has a 1 8" NPT bleed port.