Tare Weight: Every cylinder has a Tare Weight stamped on its neck or collar. This indicates the exact weight of the empty cylinder. When you pay for a refill, you should only pay for the weight of the gas, not the container.Safety Limits: Cylinders are never filled to the brim. By standard safety laws, they are filled to a maximum of 80% to 85% of their water capacity to allow the liquid gas room to expand safely.