| 摘要 |
PROBLEM TO BE SOLVED: To ensure easy removal of an inner plug by making a longitudinal cut at a lower end of an outer cylinder, making an arcuate cut on a shoulder wall, providing a cut groove connected therewith, and further providing a finger hook on an upper end of a tab formed by the outer cylinder cut and the arcuate cut on the shoulder wall. SOLUTION: A notch 13 is provided at a predetermined position of an outer cylinder 6, and an upper part of a coupling 12 is made into a cut 14 extending longitudinally. An arcuate cut 15 with a predetermined length extending in a predetermined direction connected with the cut 14 is provided along an inner periphery of the outer cylinder 6, wherein the two cuts 14, 15 form a tab 16 on a peripheral wall of the outer cylinder 6. Then, a finger hook 17 is provided at an upper end of a rim on a side of the cut 14 of the tab 16. This constitution allows the tab 16 to be pulled outward with a finger hooked on the finger hook 17 provided at the upper end of the rim on the side of the cut 14 of the tab 16 when the coupling 12 is to be cut for disposal, thus extremely facilitating handling of the tab 16.
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