The drop arml must be tightened with a specific bolt, not only must the thread match, but the length and hardness are important for correct tightening.
The bolt is secured with a locking plate, don't forget to order it (mentioned in the options tab). The locking plates are single-use, by straightening them and reusing them, you play with your safety. Remember that metal fatigue causes the locking plate to break and the bolt to vibrate.
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