prov:value
| - The expansible member 3 preferably has flexibility and can be formed, for example, by using thermoplastic resin such as polyolefin such as polyethylene, polypropylene, ethylene--propylene copolymer, ethylene--vinyl acetate copolymer and cross-linked ethylene--vinyl acetate copolymer, polyvinyl chloride and polyurethane, more preferably, cross-linked ethylene--vinyl acetate copolymer, for example,
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