WirthCo R.V. “Locking” Bumper Plug – Black is designed to securely hold sewer hoses in place. It fits standard 4 inch bumpers, has no hinges and doesn’t require any drilling or welding – just push in the center to lock. This bumper plug is weather and UV resistant and is made of thermoplastic rubber so it won’t fall out. For over 30 years, WirthCo has been a prime manufacturer of practical products for making life easier and safer. California Prop 65 – Warning, This product contains chemicals known to the State of California to cause cancer, birth defects or other reproductive harm.