| 摘要 |
PROBLEM TO BE SOLVED: To surely clamp a stem by a stem driver and to make the engagement and disengagement operation between the stem driver and a stem easy and rapid. SOLUTION: This stem 1 has a stem pin hole 2 which fits front ends 7 and 10 of the stem driver 4 in driving and is formed to a rotationally asymmetric and inwardly divergent shape. The front ends 7 and 10 of the stem driver 4 to be fitted into the stem pin hole 2 having the rotationally asymmetric and inwardly flaring shape in driving the stem are formed to a divided structure of an openable and closable longitudinally splitting type which may be attached and detached to and from each other by the operation of gripping parts 8 and 11 on a rear end side and are formed to the rotationally asymmetric and forward flaring shape to make the front ends freely insertable and removable in the state of moving the close the stem pin hole and unremovable in the state of moving to open the hole.
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