Which type of perm rods typically produce tighter curls?

Small rods are what typically produce tighter curls in perming. This is because the diameter of a perm rod directly influences the size of the curl that is created. Smaller rods create more defined and tighter curls due to the way the hair wraps around them. When hair is wound around a small rod, it bends more sharply, resulting in a curl that is compact and springy.

In contrast, larger rods yield looser curls or waves because the hair wraps around a broader surface area, leading to a gentler bend rather than a defined curl. Medium rods fall into a category that is between the small and large options and will produce moderate curls, but they won't be as tight as those created with small rods. Flexible rods, although versatile, can create different curl shapes based on how they are used and do not guarantee the tightness that small rods specify. Therefore, small rods are clearly designated for producing the tightest curl formations in perming.