Hair Digital Perm Machine uses hot rods with the temperature regulated by a machine with a digital display, hence the name. The size of the perm rod determines the size of the curl or wave. Large perm rods are commonly used to create large curls and wavy perms. If you have long hair, large perm rods are the most useful in creating lots of curl. Smaller perm rods are used to create tighter curls. The length and style of your hair usually determines which perm rod size will be used as shorter pieces of hair cannot be wound around a perm rod as many times as longer hair. Come to Vaney-Beauty.com to find the best hair digital perm machine for you！