Abstract: A method of making a sealed tennis ball container, and the container so sealed. The container is first inserted into a cylindrical canister, resting the shoulder of the container on the upper rim of the canister. After tennis balls are placed into the container, a disk having heat sealable polymer membrane material is placed on the container shoulder. An induction heat/sonic transducer head is clamped to the container shoulder under pressure, pressing the seal against the container shoulder. The sonic transducer is then energized to molecularly bond the disk to the container shoulder, to thereby seal the container from the passage of air, with the tennis balls inside. A heated probe is then melted through the wall of the container to thereby make an opening in the wall. A gas is injected into the container through the probe while still inserted in the container, to a level of pressure substantially above the final desired pressure.