PURPOSE: To prevent lowering of sealing capacity even at the time of exchange of a connecting rod so as to maintain the sealing capacity for a long time by providing a first seal member made of a rubbery, elastic body in a space between a first collar part and a second collar part, so that, when the connecting rod is exchanged, the first seal member makes the second, annular collar move upward.

CONSTITUTION: When a connecting rod 31 is exchanged, a nut 32 is released from the state of the connecting rod 31 engaged in place, and then the connecting rod 31 is removed. Then, a second annular collar 15 is moved upward relative to a first annular collar 11, owing to the restoring force of a first seal member 19, which has been deformed by the pushing pressure of the connecting rod 31. Next, a new connecting rod 31' is inserted into the tapered part 34 of the handle of a ball stud and fixed by means of the nut 32. Accordingly, even when the diameter of a through hole 25' of the connecting rod 31' after exchange is smaller within a tolerance than that of a through hole 25 of the connecting rod 31 before exchange, no gap can be formed between the connecting rod 31' and a seal member 27, even if the connecting rod 31' after exchange cannot go into the handle 3 up to the former position of the connecting rod 31 before the exchange, because the collar 15 is moved upward in advance.