The Shields Exhaust Protector Valve (4 / 101.6 mm) is designed to prevent water from entering the exhaust system during following seas or when backing down. It uses a specially compounded rubber flapper valve that allows exhaust gases to exit while blocking water intrusion.Manufactured from weather-resistant EPDM rubber with UV stabilizer, this protector ensures long service life in harsh marine environments.Features Prevents water entry into exhaust system Rubber flapper valve design Suitable for following seas and reverse operation Weather-resistant UV stabilized Marine-grade materialSpecifications Product type: Exhaust Protector Valve Size: 4″ (101.6 mm) Material: EPDM rubber Color: Black Application: Marine exhaust system Warranty: Limited Lifetime