Packaging
Before 1925, tennis balls were packaged in wrapped paper and paperboard boxes. In 1925, Wilson-Western Sporting Goods Company introduced cardboard tubes. In 1926, the Pennsylvania Rubber Company released a hermetically sealed pressurized metal tube that held three balls with a churchkey to open the top. Beginning in the 1980s, plastic (from recycled PET) cans with a full-top pull-tab seal and plastic lid fit three or four balls per can. Pressureless balls tend to come in nets or bags (since they do not need to be pressure-sealed).
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