An M6 thread has a basic major diameter of 6 mm. Typically, metric thread callouts also come with the thread pitch, such that an M6 × 0.1 threaded bolt has a basic major diameter of 6 mm and a thread pitch of 0.1 mm. When purchasing a threaded fastener, make sure you have both the diameter and the thread pitch. Without one of those measurements, you could buy the wrong-sized hardware.
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