Plastic, polished, plug with strap, for use on liquid propane cylinders while transporting, keeps valves clean, protects from leaks & protects threads from damage, for rvs. ?High Density Polyethylene ?O–ring Seal ?With Lanyard ?For Tank Transport or Storage ?Prevents Leaks ?Protects Valve Threads. For Tank Transport or Storage. O-ring Seal. With Lanyard. High Density Polyethylene. Protects Valve Threads. Prevents Leaks. Highlights: Recommended for us on LP cylinders while transporting for refilling Keeps contamination out of valve Plastic Carded WARNING: This product can expose you to chemicals including Lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. United States Hdw #RV522C Plastic Pol Plug/Strap. UNITED STATES HDW MFG/U S HA. This Is Easy To Use. This Is Highly Durable.