| 摘要 |
A writing instrument has a cap including an inner cylinder portion having an open end and a close end, a cylindrical outer cylinder portion having open ends, a plurality of connection rib integrally connected to an outer surface of the inner cylinder portion and extending in an axial direction and a plurality of vent hole respectively formed between adjacent ones of the connection ribs and a writing instrument body including a pen tip. The open end of the inner cylinder portion extends rearwardly of the connection ribs, the inner cylinder portion seals the pen tip when the cap is fitted on a pen tip side of the writing instrument body and an annular seal portion which is closely contact with an annular airtight portion on the pen tip side of the writing instrument body is provided on the outer peripheral surface of the open end portion of the inner cylinder portion.
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