What narrow-wide actually does
A bicycle chain has alternating wide and narrow inner gaps. An X-Sync ring is cut with alternating wide and narrow teeth to match them, so each tooth fills its link completely instead of sitting loose in it.
That is the whole reason a modern 1x drivetrain holds its chain over rough ground without a front derailleur or a chain guide. It is a genuinely elegant piece of engineering, and it is why single-ring setups took over mountain biking.
Tooth count changes your gearing, and the mounting standard has to match your crank — direct mount and bolt patterns are not interchangeable. Bring the crank or a photo. Related: SRAM drivetrain.
