ttnight 2 pcs Outdoor Cooking Kitchen Propane Refill Adapter Cylinder Adapter Grill connectors Lp Gas Cylinder Tank Coupler Heater Camping (Blue&Gold) Refills 1 lb. bottles in 1 minute or less so quick. Works with all 20, 30, or 40 Pound 50,Cylinders. Hook up the smaller cylinder with this adapter and it will equalize the pressure between the two tanks. With this adapter you are not able to overfill the smaller bottles it will only put in the tank as much as it can hold, you are also able to back fill into larger tank if you got in a situation where your larger tank runs dry. Compared with others ,ours has a safety feature. When flow capacity is too high, ours will automatically close at the end. This feature controls the flow capacity of the propane transfer and ensures the tank will NEVER overflow. This protects you from dangerously overfilling your tank while theirs not.