RevAir can be used on all hair lengths, from very short to very long.
RevAir needs 3" in length to feed into the mouth of the Wand and can Rev up to 6 foot long hair. Because RevAir dries hair straight, short hair may benefit from a bit of styling or shaping with other tools such as curling irons once dried.
Long hair will go through the Wand and into the Hose and will accommodate even the longest hair. Very long hair will be much less dense at the ends though so watch your speed levels to guard against tangles.