Final answer:
To achieve an even curl, you should use perm rods that match the desired curl size and hair length.
Step-by-step explanation:
When looking for perm rods to create an even curl, it's important to consider the size of the rods. Smaller rods, such as 0.25 inches or 0.35 inches in diameter, are ideal for creating tight and defined curls. On the other hand, larger rods, like 0.75 inches or 1 inch in diameter, will give looser, more voluminous curls. It's also worth noting that the length of the hair should be taken into account when choosing perm rods. Shorter hair typically requires smaller rods to achieve an even curl.