What the 12-inch and 18-inch labels describe
Use overall length for storage and ask about other dimensions separately.
Read one number at a time
The Classic is listed at 18 inches and the Junior at 12 inches. Those are end-to-end figures. Ask about the maximum width and how the maker recommends storing the flexible material.
Check material and care on the exact package
Match any cleaning and storage directions to the model and variant. For a comparison with different shapes and materials, see the double-ended design guide.