Features: Compatible with all 20, 30, or 40-pound 50-cylinder tanks. With this adapter, you cannot overfill the tank. Smaller cylinders will simply sit inside the tank as they fit, and you can also backfill into larger tanks if you find yourself in a situation where your larger tank is running low. The hook on this adapter balances the pressure between the two tanks. Compared to others, we have a safety feature. When the flow rate is too high, it will automatically shut off at the end. This feature controls the flow rate of propane transfer and ensures the tank never overflows. This protects you from the danger of overfilling your tank. Note: To use the adapter, the cartridge must be 1 pound from a 20-40 lb tank. Important tip: Always start with an empty cylinder. Before refilling, chill the empty 1-pound cylinder in the refrigerator (for optimal filling) for 15-20 minutes. Fill the larger tank at room temperature (not exceeding 85°F). Specifications: Product Name: Propane Refilling Hose Length: 3.5FT Material: Copper alloy and stainless steel Weight: 500g Application: 1-pound propane cylinder refilling adapter Function: Features a safety automatic shut-off. MOUNTING TIPS: Connect the left-hand threaded lug adapter to the tank. Connect the right-hand threaded cap of the adapter to the 1-pound cylinder (tighten by hand). Close the 1-pound cylinder and invert the tank. Open the tank valve for a few minutes until you can no longer hear propane transferring. Then, close the valve. Return the 1-pound cylinder to an upright position. Disconnect the small 1-pound cylinder first. Check the 1-pound cylinder for leaks: apply a small amount of soapy water solution to the cylinder opening and safety valve. If bubbles appear, dispose of the small cylinder in a safe area. Package Includes: 1 x 3.5ft propane filling hose